I am new to this forum in particular, but I have taken two 'cycles' of XFA. It's main ingredient is Arachidonic Acid, which from what I understand is just an Omega-6 fatty acid. The 6s are the inflammatory, omega-3s are anti inflammatory.
The idea behind it is that it inflames your muscles more than normal during your workout, which damages them more, and leaves more room for building during recovery. As a convenient side, the pump that occurs on a regular workout is unreal -- I literally felt as though my muscles would just split the skin down the middle.
Many users report increased DOMS, and though I did feel that a little, I did not get it near as much. About 14 days in the pumps start increasing (difference is night and day), and probably around 18-25 days in (halfway mark, usually run 50 days), is the golden age of XFA. The strength hops up, and the body weight comes in a little quicker than normal.
The results are not miraculous, and they don't claim to be. Just solid, consistent, predictable results, which I feel is tough to come by when you talk about non-hormonals (take my credibility into account though, I am only 21, only been lifting 4 solid years).
Both times I did my 50 day runs I put on about 5 or 6 lbs, obviously not totally lean in only 50 days, but as an ectomorph, lbs are hard to come by.
Now, inflammatory fats don't selectively go to your muscles -- you must be careful with your joints as well. mobility stretching before lifitng is crucial. I sprained my ankle severely on my first cycle on day 36 and it swelled up like a damn balloon and hurt like hell (way more than past sprains)-- so you have to be pretty careful.
I dare say I can answer alot of questions you may have, but I am in no way at all affiliated with Molecular Nutrition, the company that produces it.
I also logged both runs on BB.com, shoot me a pm if you are interested to see them. Hope this helps!