Unable to dim with a standard dimmer that works fine with halogen bulbs
933713
Supposed to be dimmable, but dimming function is unusable.  Any setting other than on full results if a very dim flickering light.  Saame dimmer works fine with Halogen bulbs.
2540131
The bulbs produce great, warm light but they are NOISY and FLICKER terribly on a dimmer even when not dimmed!!  I have tried now two different LED compatible dimmers (including the newest and most expensive Lutron) that have worked with other LED bulbs much better than these.  I will not purchase these for a dimmable area again.  I moved them to a standard switch and they are quiet and fine.
4847512
The description says the unit is dimmable, but the lamp, even as expensive as it is, has no dimming capability.  I think they meant a dimmer could be added (if you can find one that works for 12V halogen), but it wasn't clear.  An in-line switch is included but not installed on the cord.  This means you have to install the switch yourself, but it also means you can put the switch right where you want.  All in all, pretty expensive for what you get.
3221723
This bulb is reasonable bright and is dimmable; however, I am only giving it 3 stars because it will not completely go dark in my fan/light fixture unless the power to the entire unit is completely off.  This means I cannot operate the fan without having some light (although very dim light) on.  When using a halogen bulb, I am able to complete turn off the light while still using the fan.  Not sure if it's a problem with the fixture but this LED bulb just doesn't work for me.
590068
Unfortunately, they don't seem to work with the halogen track lighting in my kitchen. Very bummed. Light is a bit whiter, not a typical LED bright white, but they are clearly noticeable when compared side by side to the halogen bulbs.  Problem is they turn off randomly for 30 - 60 seconds, then turn on again.  I've tried every bulb and every light fixture in the track, and they all blink.  I've read that some LED's are not compatible with certain transformers used in halogen lighting. I don't know if it's a manufacturing issue, or a technical one. But, these won't do for me.
1861480
This bulb doesnt work properly with a dimmer (specifically one by Lutron). Unlike the very old LEDs I have and do work fine. This LED will not go off totally! All the other lights go off but this one glows and flickers! Major failure for me on this end! That I cant turn the bulb off completely is the reason for the 1 star. If anyone is interested in the measured SPD, heres what it looks like, measured using a Spectrophotometer.

Update: I may have been harsh with the 1 star review based on issues with my dimmers. But I think its very important for customers to know, IF they intend to use these bulbs with a dimmer, make sure they work! I received a number of emails from the company saying they would replace the bulb, take it back etc. Very accommodating. They ARE trying to stand behind the product. Since I moved the bulb to another room without a dimmer, it of course now turns off as it should. Now should the company attempt better compatibility with existing dimmers? Yes.

So Im giving them a 3 star review (3.5 if I could).
4089392
I would have given these a four:  great white color, cool operation, fast shipping, good price, same physical form factor as standard MR16 halogens, slightly brighter than the 50W narrow beam halogens they replaced; not a five, because they have a limited dimming range (they don't get much dimmer than 50%, even when the control is all the way down).  However, it turns out they are incompatible with the Lutron wall switch dimmers in our home.  Hence the 2 rating.

I wanted to use them in a string of 6 recessed lights, and I swapped in one; it was fine.  The dimming range is limited, the dimmer has 24 levels, but below about 15 these bulbs just stop dimming; the halogens I had in the same string dimmed all the way down to an orange candle-light glow.  On the plus side, the light color of these LED lamps doesn't change to orange as they dim; on the minus, they don't dim below about 50%.

When I swapped in the rest, they started to blink slowly - about 2 secs on, 10 secs off - whenever I set the brightness above about 75%.  It didn't make sense that I could be overloading the dimmer, since it was fine with 6 50W halogens, and these only consume about 8W apiece, but I pulled out a couple anyway, leaving the other sockets empty.  Same blinking.  Pulled out all the LED lamps but one; same blinking.  Added back in a Halogen; the blinking went away.  Added back four more of these, for a total of 5 LED and one halogen; no blinking.  Pulled out the halogen, left the socket empty; blinking again.  In summary, I could drive up to 5 of these LED lamps, as long as I had at least one of the Halogen bulbs in the string.  But I couldn't drive even one of the LED bulbs if there were no Halogens.  Because of the huge difference in brightness between these LED bulbs and the standard 50W halogens when not running close to 100%, leaving one Halogen in the string of LED lamps was not an option.  So now I'm shopping for a dimmable MR16 LED bulb that is compatible with Lutron dimmers.
633116
I previously bought several Philips LED lights and found out that my Lutron dimmer switches (although LED compatible) did not support them (rapid blinking).
I decided to give these a try and so far, they seem not to have the same effect.
546640
These bulbs have not worked well at all with my Lutron dimmer.  I tried other LED lamps that worked fine with it.  Light output is good.  Supposed to be about the same physical size as an A19 (standard home) bulb but they stuck out of a fixture I installed them in.
1918331
These bulbs are VERY bright. They say 40 W lumen equivalency, but they are painfully bright in my bathroom vanity. So I went to Lowe's, and stood for 30 minutes trying to find a compatible dimmer. According to the product details, the Lutron DZVWCL-153PH-WH is compatible.
NOT SO! As soon as I turned them on, there was constant LOUD buzzing, even when the bulbs were not dimmed.
Unfortunately, I bout two six-packs of bulbs and the dimmer set me back another $25 dollars. So now I'm out $85 and I have to find a new solution. I also thought maybe there was just one or two bulbs might be defective, so I unscrewed them all, and screwed them in one at time. Every single one buzzed. All eight of them in one bathroom sounds like a nightmarish beehive.
319557
I replaced a chandelier and wanted to used LED bulbs, however the old touch dimmer switch didn't work with LEDs. The stores don't stock the traditional Ivory color dimmer switches so I bought it here. The dimmer works well with the LED bulbs, and the low level is adjustable to customize it to the bulbs' performance.
2379331
Controls fan well, but the light dimmer is no good. Ive tried it with several brands of LED PAR20 bulbs, all with unsatisfactory results. Some bulbs would dim but wouldn't turn off completely, others would go off prematurely. So far i haven't found a combo switch which handles LED/CFL lights well.
1296399
The light color and brightness is great for this little LED.  It advertises 3000K color temp., which I believe to be accurate. The problem, which I cannot definitively attribute to the bulb is one of robustness/compatibility. I installed 2 of these into 20W halogen puck lights that are installed in a bookcase I own. The halogens burn a lot of power and create a lot of heat.  I didn't like the idea of leaving those on for the look every day from dusk till dawn. So I've been looking for an LED replacement. Theses little guys are large enough that the cover wouldn't fit any longer while these are installed. This wasn't much of an issue to me since you don't really see that unless you purposefully look for it. The problem is with the compatibility. The bookcase has 2 puck lights on a system that has a 3 position dimmer, which is cycled with one of those touch pads. So you touch once each for low-med-high-off.  I don't know if it's the bulb or the LED's compatibility with whatever type of dimmer the manufacturer of the bookcase used, but when I installed, I first noticed that instead of off-low-med-high, you get really dim-dim-bright-really bright. The high setting with a halogen is equaled by the med setting with the LED. But in the brightest mode, the LED flickers really badly. So I left it in the med setting, which was bright enough for me. But when I came back an hour later to check on it, it had somehow switched itself to a lower setting. Then in the morning, it was off completely and the LEDs no longer worked. I re-installed the halogens to check the circuit and they worked fine. So the LEDs seemed to have broken. I've since resolved to replace the entire system with a natively LED puck light system with it's own dimmer function. I happen to have a few left over from a cabinet lighting project. They're awesome in case anyone is looking for such a thing. They're American Lighting LVP-5KIT-NK.
3646502
Luton documentation on this model indicates it should work with dimmable CFLs and LEDs. I have a dimmable LED bulb and it didn't get nearly to full brightness.
1688667
I bought the soft white bulbs. Ive always trusted Amazon basic products, but this was a no go. I needed dimmsble bulbs. Using these with GE smart dimmer switches, I get buzz and flicker. At even lower dimmer settings, they will flash off and on. Useless to me as dimmsble bulbs. They are quite bright at their full brightness if thats all you need. Skip these if you're looking to use a dimmer.
2013631
Inclusion was a pain, but I finally got it working with my Wink hub, although the switch's led never blinked during the process.
Dimmer works fine, although it takes quite awhile for the light to turn on to full brightness and to turn off. I wish the ramp rate for brightness was faster.
4030210
Sending back as they were way too bright and don't work well on a dimmer.