My 20D was broken right out of the box from B&H - the viewfinder LCD produced garbled nonsense for the aperture and shutter speed values. Unfortunately, I didn't notice it right away, so I proceeded to install the Canon software, and THEN I noticed. B&H wouldn't take it back because the software was open. I called Canon and the first person I talked to was inept at best, telling me that the newest available firmware was 1.1.5, even though I had 1.2 on my camera! I called right back and got a much more capable individual - they sent me a pre-paid shipping label, and once I mailed the body out, I recieved it back repaired in 7 days - much less than I expected. The moral here is: don't open the software until you have tested absolutely everything. If you do, forget returning it to your dealer, even if they are reputable. And if you do have to contact Canon, multiple calls may be in order. Eventualy, it was well taken care of.
Regarding failure rates - I work at a camera store, and I have dealt with more faulty 20D's than all other Canon SLR's, film or digital, combined. I believe they are (or were) being rushed out to meet initial demand. The entire first "wave" that we received before Christmas all had a crooked rear LCD - not a major problem, but an annoyance when you just spent $1500.00, and a major clue as to how strict their quality control is. After all that, I love my 20D, but I will definitely be more careful in the future before deeming a camera "OK" and loading the software! (which I've never even used anyway!)