I've tried aniracetam, noopept, and piracetam. Out of those I can recommend noopept, 30mgs sublingual hits pretty good, makes me more focused. Personally aniracetam just makes more more sociable, but that could be placebo. Still want to try oxiracetam and phenylpiracetam but haven't had a chance.
Racetams don't cause dependence and don't seem to have any associated toxicity.
Choline is pretty necessary with racetams if you don't eat a diet with a good amount of choline, which is basically meat and eggs. The "sense of impending doom" goes along with the choline induced depression that can happen if you take a large amount of it daily. If you keep it to less than 3 grams of choline citrate a day you won't run into that, and if you do all you need to do is stop taking it for a few days to go back to normal.