I originally thought i'd bypass Steam by buying HL2 retail in stores... boy was I wrong.
Keep an eye on the port activity light of your router or switch that your computer's plugged into... I did... and while I'm playing HL2, i see that little light blinking like crazy, when the only thing running is HL2 and it's "companion" Steam. I don't know what it's doing, but i don't like it. As was mentioned, I've got no problems with the game validating with a server every time you want to play online, to make sure that no two CD keys are in use (like Blizzard does with their games), but they make the game too "online oriented"... I mean with 5 CDs, I'd have thought I could install it, MAYBE verify it... I can still see that... because I can see how they don't want someone installing it on 10 computers... but the whole "logging onto your account to play the game"... that's bull crap, and I don't like it. I mean, when I click on "Half Life 2", i expect the game to pop up, not some little turquoise box to pop up saying "Logging into your account..."
*shakes head*
otherwise, the game seems good. I'm not happy with my framerates, but I suspect it's my crappy 9200. When you run the "Frame rate test", what FPS are you all getting?
Overall, great game, I'm loving it, but Steam i don't like one bit. It's taken to extremes, and it's not like it's going to stop piracy of the game... or if it was supposed to, then it's already failed in that regard.