Developers can choose to use the XBL servers or p2p, whether they choose to do one or the other isn't MS' place to say -- so why bother flaming MS?
Why don't you guys just give it a rest, huh? No point in these trolls.
I've been playing the beta now for a couple weeks. I'm not sure if it's p2p or client/server for each game, but it's relatively lag-free and a very good experience nonetheless.
Perhaps if you guys played a game in specific that you found to be laggy because they implemented in a p2p fashion you'd have a case to complain -- but to the developer, not MS.