I really like Damage Industries, but on some items you really have to watch out or you'll end up receiving black oxide finished parts instead of proper phosphate finished parts. And most of their parts don't even offer the option, just black oxide only.
I like to use their buffers and most of their springs seem to be good as well... I prefer to stick with their stainless springs though.
Other than that they usually ship pretty fast and their packaging is very good.
Having said that I still prefer to sick with Colt for a lot of parts, but I do like what I see from Windham Weaponry enough that I may start to go with them on more parts in the future as a substitute of sorts.
RRA for roll pins simply because I prefer the coiled type roll pins for trigger guards, bolt catches and forward assists.