I drive 2560X1440 all the time. At work I have an ACD, and at home I have a ATD. Both work fine with my MBA. I also have an HP 2560X1600 30" display... but I am not using it at the moment. I keep it in a secondary office that has been going unused. That monitor uses a mini-display port to dual-link DVI adapter as it only has the DL-DVI inputs.
/Jim