Yea, its pretty good. For a free service, its actually really darn good. I like PnPG for all the gamer discussions, and OP for the campaign management... glad they've teamed up.
It was a team up that just made sense based on what OP's goals were with being able to offer some sort of player matching widget for their members. Much of that happens behind the scenes, but from what I have seen, it has been a great boon for players and DMs from both sites.
I've started using OP to manage my 4e campaign.
My only reservation is with myself and not being really familiar with how to use the wikis, the coding, etc. I need to learn!
This is turning out really well for me. PnPG i've come to appreciate more for the social aspect and OP for the campaign management. Though they overlap in in some areas, i've decided to focus on PnP for discussion threads because i feel like there is more of a sense of community here. OP is just way better at campaign management. I especially like the map handling.