i'm in a group with two friends; one really close friend and one who i'm friends with but dont socialise with much outside of school... we've gone together before for group projects and although we knew that 'friend' groups dont always work out, we've done fine. We know each other's strengths and weaknesses, what we all can and cant do, who is comfortable with what, who has what resources etc (eg my house has the most practical rehearsal space and another member has a seemingly endless costume box)...and although in the early stages we got a bit distracted and fought over ideas, once we had agreed on what we wanted to do it was great, we just got ourselves into gear and did it. motivation is a key thing regardless of social ties, if you're not committed to the piece then it will eventually suck no matter how close you are. i think an advantage of being in a group with friends is that it is so much easier to discuss things and brainstorm and argue (lol) without feeling like you have to be all polite and diplomatic all the time about it. plus you automatically feel more comfortable with people you know and like; it's fine to expand and work with unfamiliar people - last time i did that it was brilliant fun - but the more at ease you are with your group the further i think you will get in the long run. and besides, if your friendship falls apart over GP, then it probably wasnt built on very strong foundations to begin with.