I use my cell phone with tethering service enabled while I'm at work for general browsing. I actually find I do quite a bit work-related browsing on it (Blogs are blocked by the work network - guess where lots of very good information about coding comes from?) Anyways, I have tried booting WoW before, and aside from the fact that have far too much work to do to be playing WoW at work, the latency is pretty high. Somewhere between 600 and 800 average if I remember correctly. I don't think aircards get better speeds, they're on the same network after all.

If you have a cell phone, be sure to look into tethering service. It's usually around 20-25$ on your cell bill, which is more cost effective than getting a separate account set up for an air card you can't use for cell calls too.