Either direct USB or a card reader will work just fine. The direct USB connection to the camera is (generally) much slower, but is safer for your memory since handling is the major cause of failure. If you are carefull, that isn't a big issue. If you are not carefull, you are likely to have problems whichever way you do it. I use the camera's USB connection and haven't had a problem in four years.
If you have another use for an AC adapter (studio), I'd suggest starting with using the camera's USB connection. If the slow transfer really bugs you after doing that for a while, then get a card reader.
Pay very close attention to Mikefellh's last two points. Doing otherwise is one of common sources of problems.
1) I prefer using the reader over the camera because the reader is usually faster than the camera connection. Also there's less risk of frying the camera with the USB connection.
2) When it comes to transferring files, I COPY, not MOVE the files...this way there's no writing to the card unlike a MOVE command which deletes files as you go...in the case of your computer locking up, or a brownout, you would still have all your pictures on your card and there's less chance of corrupting a card. I only erase the pictures (using the camera's erase/format function) AFTER I make sure they were transferred properly.
3) Format ONLY in the camera. Computers, especially XP, can corrupt cards.
I should add that I haven't lost a picture in two years in following this proceedure.