Have to say my mac is working fine for playing Serious Sam 3, Path of Exile, Dota 2, Neverwinter, StarDrive, Civ V, any Valve game really, Borderlands 2 runs amazing, and plenty more.
In fact the only game that didn't work for me was Poker at the Inventory, but apparently it doesn't work for most people on MACs according to the steam forums.
Does it all really well. Sure it's not a gaming desktop, but it was never supposed to be.
The laptop should be fine for any COD game considering how old the engine is, but I'd say on BF3 you'll have to turn down the resolution and settings quite a bit. You won't be maxing out any graphics unless the game is a few years old.
I have to say though, I've been extremely impressed by the rMBP. I have 123 Steam games, 43 of which have native mac Clients. Others have mac clients which aren't on steam and the rest like Dota 2 and Neverwinter work brilliantly through wine without any performance issues.
Just head over to The Porting Team, for amazing wine ports of retro and new games.
My biggest gripe isn't with the laptop and is with MS. Especially making you pay for a Mac version of office when I all ready own an Office 2010 Pro package with multiple licenses. I'll get office 2011 eventually, but until then Pages and Numbers have done me fine.