Gotu Kola, as far as I understand, is widely considered a good herb for meditation in eastern medicine.
So I tried it, and unlike many other herbs and supplements I've tried, there was a definite noticeable effect.

It seems to increase mental energy, and also make you a bit happier, but the effect are temporary, and overall very similar to caffeine in my opinion (with a "low" period after the effects wear off, with the intensity of both the low and the high being proportional to the amount taken). The general recommended doses will produce very subtle effects, but you can take much more for more intense effects. Overall, due to the "low" after the high I think it should be used for short periods of meditation where you want to get the maximum value out of the meditation period, but don't care too much about your mind state afterwords. 

Just a quick description of my experiences with it (I am actually growing it in my appartment right now, much funner than buying it at a store). Enjoy.