Well I just bought the 10-22 EFS

Congrats, I love mine and with the 24-70 range in the bag it makes a good companion to it. Variable F stop does not bother me with this lens and I can always set it to 4.5 if I don't want it to vary when I zoom. I don't use it very often but it's great to have sometimes.

How good or bad is it as far as distortion goes?

I'll make an arguement that the 10-22mm will fetch the greatest resale value if anyone goes full frame and needs to replace the lens. Thus it may or may not be more economical to own over time then a 3rd party APS-C wide angle lens. However the lens is so light, I'd be tempted to leave it on a 1.6x frame (like a drebel) and never buy a FF wide angle. This is the one of two EF-S lenses I always wished Canon to build. Now if they would just make an 18-70mm constant aperture lens with near L optics I'd be so very happy, f4 would be fine if the thing was 10-22mm light, and 10-22mm priced.