I don't think I've ever seen an external USB2 hard drive (regardless of model or the speed of the actual drive), with speeds above 30MB/s on a desktop-based copy. Usually they top out around 28-30. In my experience, USB is next to useless for large data transfers unless you're willing to go away for the weekend - or at least go to sleep for the night.

But if I could get close to 30MB/s with a thumb drive that would make me super content.