Instruct: Classify Amazon reviews into positive or negative sentiment
Query: Effective, but...

You can definitely feel an effect from this stuff... but for me, it was not desirable. I felt jumpy and anxious, with a knot in my stomach; it makes me feel hot, then cold... like I'm having menopause or something. Made it hard for my eyes to focus, and sometimes the things I would look at would "crawl". Didn't really give me "energy" to work out or get chores done, but it did prevent me from sleeping. Often touted as increasing sex drive, I noticed no increase in sexual function. Maybe it affects different people in different ways, but it definitely does something.