Steam's working fine. There were a bunch of last-minute preloads going on, even though Valve upped the available bandwidth--so after HL2's launch, they increased the bandwidth even MORE, by as much as 50% on some content servers.
Valve has gone some serious power on their Steam servers.
Some intermittent glitches earlier today, though. I came home and tried to start Steam up again - it asked for my PW this time, which I couldn't remember for the life of me. So I resubmitted my username to get the code for changing the PW, and it couldn't find my account name to redo the PW, despite the fact that I got an email from Valve referring to my account name just this morning. Chalked up to network/server bugs, went out to dinner, came back, and now it's working okay again...