On the T1 here at school I get excellent throughput on Steam (1 mps), but Steam is definately not without its flaws. Crashing, having to reinstall is not uncommon. At the same time, though, it's kind of nice to have my account completely portable and being able to sit down at any computer, download steam, download CS and play. Setting up a computer doesn't take more than a couple of hours.
I'm going to buy HL2 in stores, though. I'd like an actual CD.