Not at all. I recommend them for use, because you get a lot faster export times with rekordbox then usb2.0. The faster stick seems to be the sandisk extreme cruzer usb3.0 64gb.
But... If you want the fastest think you can get, with the fastest load and search of mp3's when using the cdj's, then i recommend ssd drives with a good usb3.0 2.5'' case.
All depends from the money you want to spend.