these things are so subjective, we all want different things at different times, and the dynamics of any group vary so much, and effect us all in different ways.
for me though, id not join a covers band who where not already organised and gigging or in the process of doing so, unless it was with people I know or have some common ground with and the being part of it/practicing was a worthwhile fun or social activity within its self, gigs then would only be a bonus.
joining in with a group of disorganised strangers does not appeal to me, even if they have good intentions.