bit of an old thread, but thought i'd pipe in with my experiences with kava since it's getting mentioned a lot. oh, and hello, this is my first post!
i've tried about 4 different varieties of kava powder and one type of kava pill, so my experience is limited to that. the kava pills i took didn't do anything for me at all. they weren't particularly high-grade, so it could just be a lack of potency, but i did a lot of research on it beforehand, and came across many comments to the effect that the pills don't work but the powder does, so i didn't really pursue pills any further. YMMV.
Now, the powders were completely different. Here you could really tell the difference between a high quality powder and a cheaper one. First, making a drink with kava is a pain in the ass. It's time consuming and annoying - it's more of a social/ceremonial drink historically, where the preparation is all part of the experience, but if you're taking it by yourself, then be prepared to spend 5-10 minutes mushing this stuff by hand in what quickly becomes a pretty tedious process. And it tastes absolutely awful. However, with good quality kava, you can really feel it after a couple of glasses. It makes you so relaxed, yet completely sociable and with full mental acuity still intact. It's sort of like pot's relaxing affect but without any of the mental clouding. The cheaper stuff just did not do this anywhere near as well. It pretty much seems to be you get what you pay for with kava powder. Also be warned that when you're drinking it your lips will go numb for a short period of time. It's not unpleasant, just weird if you're not expecting it.
Now, the problem is I really don't like the taste. Many people say they have gotten used to it, or have tried mixing it with juices (which i've tried, but it still tastes awful), and the thought of drinking it kind of turns me off enough so that i don't really take it anymore. So I'm back to trying the pills... I've just ordered the highest-potency ones i could find straight from a farm in Hawaii that makes some pretty good powder in the hopes that maybe it will work - although it's more of a shot in the dark as apparently it is the masticating process when making the drink that releases the kavalactones, which is the active ingredient.
Will let you know how it goes when they get here.