I just joined Power Play today, for the missiles. Is anyone doing it?
By "the missiles" I'm going to assume you mean packhounds? I just got mine - you're going to love them, they're juicy and sweet
As for the rest of PP, there are some adherents, but many folks have also moved away from it. I just use it for the gear now. The problem I found is that it seemed really promising at first, but after a couple of weeks it really lost its luster. There are many things about PP that could have made it (and by extension, the core game) much more engaging. Still, you might enjoy it - just give it a shot and see. Also, get yourself some pacifier frags.