Phosphatidylserine has a lot of research to back it up.  It reduces stress, improves cognition and makes you shit-bricks for England (or whoever).

Here is a link to the study about it reducing cortisol levels when exercising intensely.

“The findings suggest that PS is an effective supplement for combating exercise-induced stress and preventing the physiological deterioration that can accompany too much exercise. PS supplementation promotes a desired hormonal status for athletes by blunting increases in cortisol levels.”

Here’s a similar study – http://link.springer.com/article/10.1007/BF00280123

“The results suggest that chronic oral administration of phosphatidylserine may counteract stress-induced activation of the hypothalamo-pituitary-adrenal axis in man.”

A lot of the nootropic/cognitive enhancing properties of Phosphatidylserine have been studied on the elderly, or rodents.  In fact, I can’t find a study (having looked for 10 minutes) on healthy, young or middle-aged people.  However, from personal experience, I definitely think it enhances speed-of-thinking and memory.  Perhaps by reducing my stress levels, I think in a more structured, and less hurried manner.

There are also a number of articles about Phosphatidylserine improving cognition:

“Phosphatidylserine supplements repair the inner membrane of brain cells. Healthy membranes can greatly improve the overall clarity of our thoughts.”

Although I would take those articles and the claims within them, with a pinch of Himalayan salt, given that a lot of the article-writers, also sell the product.
The main downside for me, is that it does give me horrendous wind.  So I’m not going to use it all the time – just on special occasions.