I and others have experiences poorly fitting pipes and silencers made by FMF - not as much of a defect but enough that will make you spend a few hours messing with it to fit well...
IMO, FMF is too much of a (dare i say) fashion statement. Ok, yes they do make stuff that pro's think are good enough but it seems that they spend alot of their resources creating a certain image to appeal to buyers.
I'm running the fmf gnarly and power core 2.. they seem to work great. Fitment was great and a very easy install. Quality appears to be good too. I've owned a procircuit before. I think I like the fmf better.