I tried it. I noticed nothing at all -- not at first, not after a while, not at low doses, not at high doses. Your mileage may vary, but I got 0.00 mpg.
My husband and I just started it 2 days ago. He thinks he can concentrate better at work now (might be a placebo) but I haven't noticed anything at all yet. It tastest like shit!
I've been taking it for a few months now, and I have noticed the results from it. I am more focused on things in general now, and can concentrate on something till it's finished now. Also my night vision has improved drastically, which is important for me as I work nights and my job involves driving.
Piracetam + Choline = goods. Piracetam + Alpha-GPC is better, though I've never tried it (heard much on the topic). Always take a good choline supplement with piracetam.