My first game on Steam was Counter Strike, but I had already been playing the retail release for a while. They had some one-time activation to bring over your CD key. When they launched Steam, it was horrible. Remember, this was the time of single core processors (Pentium 4), so any anything that interrupted the cpu would effect your FPS. Plus it was buggy and crashed all the time.
I boycotted Steam and Valve and kept playing pre-steam CS 1.6 till the Orange Box came out. But TF2, Portal, and HL2 plus episode 1 was too good of a deal to pass up, and I had a new AMD Athlon that felt like a beast at the time.
Kinda sad I forgot my original account, would have been neat to have an account as old as Steam. Oh well.