Also had a sour Armslist experience recently, though nothing like some of the other crazy stories I've read in this thread. I think the wackiest experience I ever had on AL was someone wanting to trade me tattoo work for a pistol I had listed.
As others have said, lesson learned, I'll stick with the gang here, and stand behind the 50 post rule all day long. It's not a slam-dunk, but it does give you an opportunity to get to know who you're dealing with a little bit. I've done a few trades/purchases with INGO members, and *every single one* has been a buttery-smooth and pleasant experience.
It may not be perfect but it much better than rolling the dice with a complete unknown on CL or such.