Just upgraded my external back up HD's to USB 3.0. In my home network, one desktop and my laptop already have USB 3.0 ports, but I had to add a USB 3.0 card to my other desktop (simple, quick and cheap).
Reports vary as to how much real world speed increases you can expect from USB 2.0 to USB 3.0. I did a quick and unscientific test by copying a large file to 2 different external HD's. USB 2.0 took 9:30. USB 3.0 took 2:15. Not the 10x speed increase that is theoretically possible, but still, a significant and certainly noticeable increase.
I've been using the built in card reader on my desktop that I use for photo editing, but now I am wondering if it would make sense to buy an external USB 3.0 card reader. There is a Transcend model over on Amazon that is pretty highly rated, and it's under $20. Thoughts?