An interesting conversation, this. But I'll tell you what, though...
I am currently going through a search for to be expanding my roster of singers and players (players mostly), and I decided to subject myself to the cattle call I have long resisted... placing ads in the local music rag and on their associated website. I have a buncha male vocalists, a couple of female vocalists and a pile of players who have trudged through my studio these last couple months, and I have shocking revelation to share:
Musicians who play with other musicians all the time are just as bad if not worse than musicians who don't. Unfortunately, they IMAGINE they are better.
These guys have all been members of gigging bands who play out many times a week, get glowing praise in the local "WhatzUp" free weekly, guys who have been told over and over again that they totally RAWK the house, dude... and they stink. They don't play in time, they don't play in tune, and they all think they are absolutely the sland. When I have to tell then that they have a bit of a timing problem or their vocals are "pitchy" (I don't watch American Idol, haven't even once, but thanks to them, I now have to cringe when I use this term), they look at me as if I have gone obviously and completely insane.
So, before a Trusim In Stone gets carved here, take it from me: a bedroom player with an ear, taste and a goddamn metronome is probably going to perform better than any dozen battle-weary jam veterans. It should be obvious from the stories you're all telling here that playing out with others, even for years and years, does nothing to refine one's sense of taste or one's concept of one's place in an ensemble. You either get that stuff or you don't. And all them talkin' 'bout heaven ain't goin' there.