20D as a backup body for $200?
If you want a backup body, absolutely... noise is very well controlled to ISO 800, passable at 1600 in a pinch and intrusive/useless at 3200. t2i is about one stop better, IMHO (and consistent with dpreview's tests as well). So, whatever you are comfortable shooting with the t2i, drop ISO one setting and you should get comparable results in regards to noise. The ergonomics of the 20D are significantly better than the t2i, but significantly different to the point that it might be distracting. 20D is better built, is larger and heavier, but is more comfortable to hold and shoot with. I've used the 20D for a number of years now, and have used the t2i on occasion... the 20D is an easier camera to make on-the-fly adjustments while looking through the viewfinder (addition of the quick control dial and joystick for things like faster change of the selected focus point, ISO, etc.). The 20D has a slightly faster flash sync for slightly more usable fill flash (1/250s i still pretty limiting in daylight without an ND filter). The viewfinder is a bit brighter/more contrasty on the 20D. Autofocus performance is basically the same. Now the negatives... the obvious: lower resolution, no movie mode, much smaller, lower resolution screen. The difference between 5fps and 3.7fps should be pretty low in your decision criteria, as neither camera does a good enough job of AF tracking for that to matter in lots of situations. I'm considering buying a second body mainly for the video functionality, and am having a hard time convincing myself anything less than the 7D will be as enjoyable to actually use... feel like I'd spend more time fidgeting with settings than taking pictures (been there, done that, hated it). Make sure you check shutter count and for sensor dust though.