I was using DMAE bitartat 50 mg/day for one year. It was for me better as caffeine, piracetam, piritinol together. It was improving my concentration, mood, sleep fluency of speech and reaction time for 24 hours when I used it in single daily dose 50mg DMAE bitartat. But it causes me stomach problems indigestion and lack od appetite. Has anybody similar experience with this DMAE's side effect?

Thats pretty much the case with any stimulant. Caffeine, ritalin, ephedrine... they all cause exactly those symptoms.
The question I have about DMAE is, how different is it from Centrophenoxine?

Centrophenoxine is a great deal more potent with some different effects.

Centrophenoxine is a combination of DMAE and pCPA. pCPA seems to be able to increase DMAE ability to cross the BBB.

I've never taken DMAE alone though I took centro a few times but stopped when I read there was just as much research done saying DMAE is ineffective as there is saying it is effective.

Does anyone have a strong opinion for or against DMAE supplementation?