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?
I'm sure what each of us do or don't do is according to our own good or bad experiences with things in the past. Most are probably over-generalizations. Even though I don't use card readers because I lost four cards full of photos in card readers, I'm sure that not everyone has had the same experience. Otherwise, you wouldn't see card readers being sold everywhere. The same goes for the USB transfer from the people you've talked to. I've never had a problem transferring my pics via USB. The point is, pick what works best for you.
Some card readers can utilize the speed of higher speed cards, but there is always a bottleneck at the slowest common denominator - whether it's the camera, USB, card, card reader, HDD, etc.