Aerodynamics are ALWAYS a factor. the faster you go, they get exponentially more significant.
Another thing I think I should mention is that many of the stiffer wheels out there are aero, and thats no coincidence. The profile of an aero wheel is naturally more stiff than the same design but with a shallower rim. Same goes for strength. I've heard that a zipp 404 rim, alone, unbuilt, no spokes, hub, nothin, can take over a half a ton of weight without deformation. And they're not heavy either.