I ran Counter Strike Source as well as Half Life 2: Episode 1 yesterday on my 2.4Ghz MBP, and frame rates where anywhere between forty to sixty with all settings on high. The MBP was driving my Dell 2407WFP at its native resolution of 1920 X 1200 and I didn't suffer from any slow downs at all. I was really surprised myself, the MBP makes for a decent gaming notebook.
Just checked out the game u mentioned, looks pretty good, gonna try it out tomorrow when morning when I get home.