I guess I'll just have to buck the trend of this thread so far. I get my greatest enjoyment from playing with other muso's. There are a whole heap of factors which come into play here, but the ones which spring to mind are:- It's marvellous to learn from and teach other players. - You can play instruments that are not ideal solo vehicles. - Your fellow team members can become great friends. - There's always a group to play at your wake.
Years ago I used a Pete Seeger book to learn how to play 5 string banjo. There's an exchange recorded in this book which goes something like: Researcher "And do you read music?" Old-timer "Why heck,there aint no notes on a banjo you just play it."
Regards John