Phosphatidylcholine

Not a lot about Phosphatidylcholine supplementation. Ray Kurzweil is a huge fan as stated in his Transcend book, see that for the why's and wherefores (basically you stop producing it as you get older). Only take if you're approaching 50, and change the dose based on your age as discussed in the book. 

Caveat, research has shown however that supplementing for people who are on a meat diet causes it to ferment in the gut and produce carcinogenic compounds. However the researchers found that vegans do not suffer from this problem (I've been a vegan for 30 years), so I recommend only supplementing if you don't eat meat. I take two capsules with each meal (about 600 mg).

Anecdotal effects: improved skin. I've directly verified that supplementing restores more youthful supple skin, but if I go off I get older/papery skin. It should have the same effect elsewhere (e.g. gut, brain) since the substance is in every single cell on this planet, but I don't have direct verification of that. Looking at your skin is easy however.