i quit using piracetam+choline - way too irritable, not a happy state. found something better.
i cycle modafinil @ 50mg a day every couple days - or every few days. if i don't cycle off, i'll have insomnia. it's said to promote vigilance (hence the brand name 'provigil'). all it does is provide crisp alertness for all 16-18 hours of the day, so no drowsiness, brain fog, or what not. it is NOT a stimulant like caffeine or amphetamines, so there's no balls-to-the-wall producivity promised by it, but with a nice cup of coffee, it's a great combination. the modafinil is great for concentration/focus - i sat for 8 hours and read a 200-page book in pdf format in one sitting. not exactly productive, but that brings me to my next point.
having the ability to focus/concentrate, does not equate to automatic productivity. although you certainly have the ability to put your head down and instantly enter a state of flow with your work, you have the equal ability to be the most intensely focused procratinator on earth - watching youtube documentaries, reading forums, or cleaning up the apartment. the point is, being able to prioritize and direct your focus on important tasks is still up to you. with great power comes great responsibility.
to be honest - i can be equally productive on days with just coffee. once i'm done with my current supply of modafinil, i'll probably just stick to coffee and my biotest supplements (power drive, spike, hot-rox, etc.) i haven't tried any amphetamine-based substance like adderall, so i can't make any comparisons.