My cats loved it because there wasn't any more fighting over who ...
587195
This is the second one of these I've owned.  My first one lasted me years.  My cats loved it because there wasn't any more fighting over who was taking a turn.  They still gave each other the stink eye, but everyone was happy in the end.
3179761
My fat cat loved it (she's not really fat she just eats anything) but my other cat would not touch it.
2072010
The feral cats no longer are going under my house and not a single one was injured by the water.
773943
Well, my cats love it anyway.  They haven't yet complained.
1645976
This is the only toy my cats will play with for more than 2 seconds. They love it! It moves easily when they bat at it, at just the right speed for chasing. It makes a little noise as it skitters across the floor -- but not as much as those plastic jingle balls which my cats seem to find annoying. And I'm sure the catnip doesn't hurt ;)

Mine have lasted fine, but my cats haven't tried chewing them or anything.
4644382
My cats love this, especially the ball at the one end. Very easy to set up and is not that big so it doesn't get in the way. Very happy kitties in my house!
2579577
I saw this on lightning deal and was thinking of buying a cat tree for my cats, so saw it as a sign and jumped on it. Was so much easier to assemble than I thought it would be, I was assuming it would require power tools and was preparing for a lot more work. I had it together with the provided Allen key in less than 10 minutes, and I'm disabled. It was very simple. My cats love it! One of them was trying to climb in before I was even finished assembling it, and she's on top of it all the time. The other cat gets on it when the other cat isn't around. They don't get along very well. One thing I had hoped is that they would enjoy it together, since it is certainly large enough for more than one cat, but they don't because they don't like each other. Oh well. I'm pleased with this purchase!
2172816
One of my cats loves cardboard scratchers and got so excited when I gave this to her that she laid down on it and refused to move when another cat came to check it out. She rarely purrs, but this made her so happy she was purring loudly. I didn't even need the catnip to get her to use it. This is of good quality for a cardboard scratcher. I don't expect it to last terribly long, just because it's getting quite a lot of use, but the construction and thickness of the cardboard is better than that of other scratchers I have purchased. Will absolutely buy this again once the current one has been destroyed by my over enthusiastic kitty.
1127347
My cats enjoy the hideout in spurts. It is not something that they constantly stay on, but a few times a day they will play or rest in it. They were a little skittish of it at first, but once one cat got in it others followed. My cats are all adults, so I'm sure kittens would love this even more.  It comes with the hardware to hang it over a door, or mount it on a wall.  I chose to hang mine over a door, which was very simple to do while standing on a chair. Just hang it over the door...that simple! It would be no trouble to move it to different areas of the house if I decide to. The hideout is made well, and is sturdy enough for adult cats to play on. The bottom of the hideout doesn't attach to anything and just hangs.  If your cats get very active, the tower will sway side to side a little, but it isn't bad. The canvas roof (very top) is attached with Velcro, so it can be removed if you like. There is a hole/opening in the roof of the top level, but it comes with a small, round cover that Velcros onto the hole/opening if you choose to keep your cats off of the top of the tower. The top level has a soft, fleece floor, the bottom level has a floor of canvas, and the other levels have floors made of netting, as some of the sides do. It seems the netting is made of some sort of tough, pliable, vinyl. My cats do claw it sometimes, but no damage to the netting or to their claws has happened. Seems very safe to me.  Each level has a floor hole/opening for the cats to maneuver up or down.  Two levels also have side hole/openings. Although I use this hideout for indoor cats, I'm sure that outdoor cats would enjoy it also, as long as it is protected from the weather. It would be great for a porch or patio. The hideout arrived in a timely manner, and looked just like the picture, but was missing the two "over the door" hooks. I contacted the seller and they made sure that I received them from the manufacturer.  That process took about two weeks, but was reasonable to me. The seller also kept in contact with me, by email, every step of the way. I like good, quality items for my cats, and this tower- hideout did not disappoint me. So glad I made the purchase!

***UPDATE 12-29-2012***

***Edited to add***: To hang over a door: There are two metal hangers/hooks that you place on the upper backside of the cat tower. You then hang the hangers/hooks, with the cat tower, over the door top. The hooks will have to hang on something that is the thickness of a door...1 & 3/4 inches thick and horizontal. Any less than this, you will have to fill the void with a rolled up towel, etc. Also, the hooks are not adjustable. They are about 8 and 1/4 inches apart. Hope this helps.
1175420
I used this in conjunction with the diffuser and it really helped the cats not fight. The newer cat has been here for awhile and they are not fighting they are not best buds but no fighting.
619696
My cat's love this cat scratcher. And, I love it too because it was such a great deal at a low price! I have quite a collection of scratchers (many different types, materials and styles) and this is one of their favorite's now. I didn't realize how much fun the cat's would have with the hole in the side and the toy that came with it hanging on the inside. So, I was pleasantly surprised to see how fascinated and excited the kitties were (and still are) with the hidden toy area.  They attacked it like they were stalking and attacking prey! They love it. Great deal!
3676386
My 6 cats love these tunnels. I've watched them play alone or 2 or more at a time using the tunnels. All 6 join in when a family member also plays along. Several of my cats are large (18 lbs.) and the 13" diameter accommodates them very nicely. They run through the tunnels with no problem. They withstand a lot of roughhousing from the cats, and the nylon is easy to keep clean. I've ordered two more tunnels and saw the kitty tee connector on Amazon which is unavailable. I found out through Pet Supply Imports that the factory is no longer making them.  I'm disappointed because that piece looked like it would have added to the fun.
2921715
Great product - my cats loved it - though I feel a little jipped - I didn't get any cool magnet stickers or a pen
2868595
We currently have 2 of these diffusers in our apartment and this order was the refills for those. We have 4 cats who have always gotten along well and then out of the blue, 2 of them started fighting for no reason. I had heard good things about this product in terms of calming cats and decreasing fighting. I also heard that it can help with urine marking/spraying and furniture scratching. For us, it definitely calmed the cats and the fighting stopped. When the bulb ran empty though, they started fighting again a few days later. We ordered the refill pack and things are peaceful once again. For us, this product did not affect urine marking and only very minorly decreased urine marking. We are still very pleased with the product because our cats are happy again and all get along well again. That's worth it to me.
4555834
My dog really loves this, but the cat kicked her out.(Future attempts by dog have all been filled with head boops and mournful stares) I don't have to look for the cat anymore since she pretty much lives in this. That was fine with me since the dog doesn't shed, but the dog wants me to order her one too :)
1289025
My cats love this scratcher so much it has already caused a turf battle. It easily fits a full size cat in resting position, and they love the height. It has great balance, is extremely sturdy and will not topple. They even like scratching the lower level of the cardboard too. It has the same density cardboard as typical scratchers, which works great on the nails. I like it most because it doesn't take up any more room than a flat scratcher in our living room.
4709808
This may look like it's not much, but all three of my cats love it.  None of them are kittens, but they chase it around as if they still are.  One of them starts loudly meowing at me everynight at dinner, because he wants to play with it.  He won't shut up until we're playing.  I don't care if it is just a little wire and cardboard, It's worth the price for sure!