It's had me playing for the past 5 hours or so, and it's been awesome. A solid sequel; all the puzzles feel new. As expected, GLaDOS is a bit miffed, and keeps insulting me :(
And the game is LONG, at least it feels that way (5 hours in, at least one more section, if not more). And I'm just on the single player campaign, I'll still have to beat Co-op.
Anyway, I found the dry dock where the Borealis was built, so hopefully that's a hint by Valve that HL2:Ep3 will be the next game to hit the shelves.
I'm looking forward to the ending :)