Aperture control wheel isn't an issue if you're using full manual lenses -- I use LOMO cinema lenses on my T2i with a PL-mount adapter, so for me it doesn't make a difference.

Not having HD HDMI output isn't a big deal if you're marking focus on a follow focus system. But don't bother using the T2i as an A-cam -- use something that gives legit HD monitoring.

The mumblings about the "in-between" ISOs are true -- it does give noise. Shoot in good light.

Moire artifacts are a killer. That's worth monitoring in preview in HD. Lost a shot the other day because I didn't check for Moire artifacts in a monitor on set.