I bought the Collector's Edition today - and while I ran into some problems connecting to Steam to create an account so I can actually play the bloody game, it's now up and running and I can well and truly say it's an instant classic! The physics are just amazing, beautifully done. A truly immersive world.
It was pretty short-sighted of Valve to do a worldwide release and not have enough server power to handle it when people register their copy IMHO. For those who don't know, it's required that you create a Steam account before you can play (even single player), and Steam unlocks the game for you to play from there after you've registered and given your cd-key. Obviously it's an anti-piracy strategy, but from about a million users trying to simultaneously create an account all their servers detonated as you'd expect. I would have thought they'd be adequately prepared, but there you go.
Once you get into the game finally, it's so very worth it. Half-Life 1: Source and CS: Source are great too.