Speaking from bitter personal experience - for me it goes without saying that the band members must get on well with each other. Thats just as (if not more) important than their standard of musicianship. BUT - golden rule number one - if there are women in the band, then NO RELATIONSHIPS. If there are, just sit back and wait for the fun to begin. I´ve been in an excellent band that have folded for just that reason. And my current band is beginning to look very dicey, just when things are really starting to roll.