My group goes through a lot of campaigns, and we're trying something neat on Wednesday nights this year (and into next, I'm sure). I'm running the Hell's Vengeance adventure path (where all the PCs play evil characters) and my friend Greg is running the Hell's Rebels adventure path (a concurrent campaign where all the PCs play good-hearted revolutionaries). We have pretty much the same group in both (Greg plays in my game and I play in his) and we switch off on alternate Wednesday nights. But because Greg has had to cancel a few games, and I've been pick up a few extra Wednesdays, the "evil PCs" are getting ahead of the "good PCs" in power level. This will probably switch back and forth over the next several times, but for now...evil is triumphing! Bwa ha ha!