[quote name='GizmoGC']So I'm new to Steam...
I have a Mac and so far I bought Left 4 Dead 2. I want Left 4 Dead, but Steam wants $20 for it.
Can I buy a PC version of it (since they are cheap) and use it on my Mac via Steamplay?[/QUOTE]
Not sure about that, but Valve stated that now that Portal 2 is out, they're going to port over the remaining original maps from Left 4 Dead 1. So unless you're a fan of the mechanics of the original, you might want to consider just waiting.