Finished solo campaign Halo 3 last night and...it was fun. Any portion with vehicles was great, but the rest was just average. The levels feel very much like they are meant to be played co-op. Haven't played multi-player matches yet, but I just haven't been in the mood for that.
I'm much more looking forward to tracking down Phantom Hourglass (seems like it's sold out at a lot of places) and Folklore (for PS3 next week). I'm craving some whimsy and fantastical magical worlds now. Had enough of the shooting for quite a while. That means HL2 Orange Box is gonna have to wait, perhaps till next year or even till episode 3! That's probably fps burn out talking.