Of course now I notice the card reader comment. I have always done mine via usb cable/camera to the computer. I think taking the card out, putting it in a card reader then back out and back to the camera will do more harm than deleting images on the card ever will. I've always been paranoid about that weakening a card that I just always have a big enough card each time and never take it out of the camera and use the usb route(till the usb port failed on my T2i anyway lol).
Interesting, I'd also been coached by some more experienced photogs I've been talking with and picking their brains, that they said they never
hook their cameras directly with USB to the computers to transfer pics...that they only did it when necessary for firmware upgrades.
Not sure how much of that was superstition....but, I figured a card reader is easy to use, often faster, I have a multiple card intake on mine, so I can plug in a CF and SD card at the same time and start copying off from both....and get back to shooting while those are copying off.
The card reader seems to transfer a bit faster than directly from the camera so far for me....anyone else experience that?