Just got the 20D four days ago, my first digital SLR and I seem to have got a bad one.
When it works it is great, but every so often it locks up; I then have to switch it off and remove the batteries to get it working again. Someone said it may need more time to write the buffer to the disk, so today I waited 15 minutes and it was still "busy", so a switch off was required again. I checked the Internet and saw that it could be a firmware problem, but alas mine was already supplied new with version 1.0.5, so I'm unlucky.
I will now send it back and ask for a replacement. Although the question is, should I stump up more money to get the EOS 1D Mark II if they are more reliable or just stick to the EOS3 and carry on scanning my shots?