I was taking phosphatidlycholine for a month or so as an anti-aging supplement. Ray Kurzweil had recommended it for skin health and said that the age-related loss of phosphatidlycholine was one of the primary reasons for skin aging. He actually took IV infusions of the stuff. So I started taking it just to try it out but then stopped for reasons I'll outline below.
One of the senior members (JustAskin) on the Peak Testosterone Forum also noticed that phosphatidylcholine produced some incredible lipid improvements:
Before phosphatidlycholine: Total Cholesterol=182; Triglycerides=113; HDL=36; LDL=105
After phosphatidlycholine: Total Cholesterol=156; Triglycerides=88; HDL=46; LDL=90
Yes, those are impressive results and almost rivalthat of a statin. Is there any research backing up this drop? Dr. Davis' web site verifies these improvements, and I quote an excerpt below. (Keep in mind that lecithin is mostly phosphatidylcholine.)
"In 1958, that Dr. Lester M. Morrison, director of a research unit at Los Angeles County General Hospital, first published (Geriatrics, January, 1958) his findings that lecithin could be used to lower cholesterol levels. In fact, Dr. Morrison reported that 'lecithin was found to be the most effective cholesterol lowering agent tested.' He reported that 80% of his patients suffering from high serum cholesterol levels showed an average decrease of 41% in serum cholesterol after taking lecithin for several weeks. Instead of "blocking" absorption of cholesterol in the digestive tract as other cholesterol reducing agents did, lecithin enhanced the metabolism of cholesterol in the digestive system and aided in its transport through the circulatoiy system." 
But there are Two Potential Dangers with Phosphatidylcholine that stopped me from taking it at least for the time being:
1. TMAO and Arterial Plaque. Many health conscious men know of the recent carnitine and TMAO studies. What they don't realize is that both choline, as in phophatidylcholine, AND carnitine can increase plasma TMAO levels. Now, before I go on, I want to mention that these studies are quite controversial, and you will see a lot of bloodshed around the web on the subject. The quick summary of these studies is that meat, particularly red meats, are high in carnitine, which converts much of your gut flora to carnitine-loving bacteria that crank out a potentially dangerous chemical called TMAO.
CONS: Critics point out that epidemiological studies simply do not show a very strong association between heart disease and red meat consumption. Since red meat has the highest levels of phosphatidylcholine, then why, if TMAO is such a factor, isn't there a more obvious association? That a great question, and I am sure will be the subject of considerable debate over the next decade.
Critics also point to a very recent study that looked at the diet and TMAO plasma concentrations and concluded that "results of this study conducted among healthy adults from the general population do not indicate a strong effect of diet on plasma concentrations of TMAO, choline, or betaine, with the exception of a positive association between dairy food consumption and plasma TMAO concentrations."  So dairy is tied to TMAO and not red meat?
These sorts of issues are what are really giving the researchers fits actually. For example, there is research that shows that fish may increase TMAO levels much more than red meat or eggs, because fish contains TMAO. However, consuming fish is associated with improved outcomes. Thus, the actual causes of increased TMAO levels may not be what everyone predicted. 
PROS: The evidence is strong that TMAO can cause heart disease. I think just about everyone has that concern. For example, a recent study found that TMAO increases vascular inflammation.  Another study shows that higher TMAO concentrations are associated with increased TNF alpha levels, the diabolical inflammatory messenger at ground zero for heart disease, cancer and many autoimmune illnesses.  And I don't know of anything that increases inflammation that is not going to be very bad for your heart. Furthermore, Dr. Hazen's group were able "to establish circulating TMAO level as an independent predictor of death, MI, and stroke even in an otherwise low-risk group."  The increase in risk was pretty large - around 43%.
So one could argue: why risk consuming phosphatidylcholine until more study work comes out showing the factors that increase TMAO in the blood and how that relates to heart and chronic disease? This is basically my take on things. I am not going to risk blowing out my arteries out or potentially affecting my bedroom performance until more information about what actually increases plasma TMAO is available. Other will disagree with me of course, and that's fine: we all have to assess risks versus rewards.
WORK AROUND SOLUTION? So does this mean one should not take phosphatidlycholine? Well, I am not yet convinced of that. After all, it is absolutely critical and highly prevalent in our cellular membranes. My guess is that the issue has to do with the delivery system. Remember that Ray Kurzweil took phosphatidlycholine via IV. And this should bypass the gut issue and leave gut flora untouched and unaffected.
2. Cancer? Here is something that your local supplement manufacturer will probably not tell you: phosphatidylcholine is found concentrated in several types of cancer cells. This association is so powerful in the case of colon cancer cells, for example, that a recent study suggested its use as a biomarker of cancer. 
Of course, the question that immediately comes to mind is whether or not phosphatidylcholine causes cancer or is merely used and accumulated by cancer cells. My guess is that it is the latter. However, one pro-cancer line of evidence comes from the fact that "evidence has accrued that phosphatidylcholine, the major phospholipid component of eukaryotic membranes, as well as choline metabolites derived from its synthesis and catabolism, contribute to both proliferative growth and programmed cell death." 
Remember that I had a high PSA read and so I will not do anything that might fuel cancer. Personally, I think my way of thinking is prudcent for any man over 40, considering that about half of men over the age of 40 have small prostate cancer nodules. Again, until more information comes out, it simply does not seem worth the risk to me.
2) J Nutr, First published December 16, 2015, "Plasma Concentrations of Trimethylamine-N-oxide Are Directly Associated with Dairy Food Consumption and Low-Grade Inflammation in a German Adult Population"
4) J Am Heart Assoc, 2016 Feb 22;5(2), "Trimethylamine N-Oxide Promotes Vascular Inflammation Through Signaling of Mitogen-Activated Protein Kinase and Nuclear Factor-?B"
6) Cancer Science, 104(10, "Accumulated phosphatidylcholine (16:0/16:1) in human colorectal cancer; possible involvement of LPCAT4"
7) Crit Rev Biochem Mol Biol. 2013 Jan-Feb;48(1):20-38, "The role of phosphatidylcholine and choline metabolites to cell proliferation and survival"