Can't give you information on how Left 4 Dead plays on Boot Camp since I don't own it, but the two games I do play I push to max settings and they handle perfectly. They are Spore and Final Fantasy 11, granted these may not be as graphic intensive as L4D.
sorry to thread jack but i see you play ff11 and i couldn't PM you because your posts were so few; but what levels/race/nation/server are you?
ampidire of midgardsormr, windy rank 8, taru male, 75smn/70blm/40whm/37cor/28nin/25bst/19rng/10dnc/etc.. you?
I am on the Unicorn server; Azagar 75thf/60nin/40war/37mnk/17blm/12whm don't really get much playtime though as you can tell with only one 75.