I used a Scanlogic (now Cypress) SL811HS with a Cygnal C8051F236. I had to do a couple of weeks of rework on their demo code to get rid of bugs, but they provide drivers and some demo C++ code for the host side to get things rolling. I don't know about other peoples experiences with USB, but I found the hardest part was figuring out how to do bulk-transfers. Almost all demo code and books seem to concentrate on HID applications, then briefly mention that other modes exist. I ended up buying a couple of books and the standard--the most helpful for me was 'USB Hardware & Software' by John Garney.

Best to all,

Josh