Mac ain't half bad if you get one with the hardware capable of gaming. I have a Macbook Air Laptop with bootcamp Windows 7. Runs okay, but no where near gaming potential. I put steam on the mac and logged in with my secondary account and noticed I had portal which I never had before. I ended up going onto the same laptop with my primary account to get Portal as well.
Question though, is this a permenant game in my library now or is it like those free gift weekends where they allow you to play for a period of time before they remove it from those who haven't purchased it?