IGN has news of actual cross platform gameplay (Xbox360 & PC, no PS3...yet, if ever) of
Team Fortress 2 in an interview ---actually a preview of a preview--- with devs and the beginnings of the dispute with the mighty Microsoft
(see Next-Gen) about the implementation of Live accounts and the fees they will entail through tie-ins with Windows' / Vista's Live gaming.
Valve is clearly siding with Epic and the same issues confronted with the Gears of Wars map pack: Annex for the Xbox360 and that has been released to the community for added $$$ in the Live coffers.