If there's one thing that personal 3D printer operators dislike, it must be the evils of warping. Warping, the phenomenon that occurs when a coincidence of material, temperatures, extruder speed and stretching results in printed models that have curled up corners. Typically warping is much more prevalent with ABS plastic and this may have led some people to switch to PLA as their primary print material.
But all is not lost. MakerBot has posted a very comprehensive list of all known techniques for minimizing warping if you insist on printing in ABS. Some of the techniques are obvious (slowing down your extruder speed to reduce the "stretch" factor) and some not so clear (adding anti-warp pods to the corners or reducing fill density). These may not eliminate warping, but they'll provide you with at least a chance of doing so.
One more thing: We lied. PLA does in fact warp. It just doesn't warp as much, but it does come in some very cool colors.