I agree that comunicating from a micro controller to Pc via USB can be a daunting task, I had a project a few years ago were i had to communicate to the PC via USB and opted for the easy way out. An USB to RS232 Converter, this gives you USB connectivity and up to about a 1Mb/s transfer rate posability, with the ease of using the old well known RS232 protocall. Loads of information can be found on all tipes of port interfacing on the following website: http://www.beyondlogic.org/