I bought an m11x a few months ago with the core 2 duo, and it certainly is the best computer I've ever owned. Some days I arena and raid on the couch while watching TV, and other days I play while the laptop is connected to my 24" screen. This thing can handle pretty much anything. I would caution you on the i5/i7 however, since those will make the laptop extremely hot.

I tried to multibox 5 wows on it, and it worked fine for the raid weekly. It certainly handles 1 WoW without any problem on max settings.