Hmm, late november...actually that works out perfectly for me, since I'll probably be playing Kingdom Under Fire until November 9th, and then Halo 2 until November 26th
And 19 hours isn't too bad. That's longer than Doom 3, and from the look of it actually has varied environments rather than just endless corridors! But remember that the people who beat it in 19 hours were fairly dedicated game reviewers, Valve was probably giving the "average gamer's completion time" when they said it would take 40 hours. Kinda like how they were saying that FF7 was a "70 hour RPG", yet I beat it in 35, or how the back of the Soul Reaver box touts "40 hours of gameplay", yet I beat it in 12 hours and got the rest of the optional stuff in another 4.
Although I hope they release the SDK for it soon, if for no other reason than to get some multiplayer mods out there (not a big fan of CS:S).