On a related note, I also recently purchased a USB-serial dongle.
The bluetooth ones I got earlier appear to have tiny buffers, and drop characters at 115200, though they are good enough for the empeg connection regardless.
So I tried a couple of the $10 adapters, and neither of those could manage even as well as the bluetooth dongles at 115200, let alone at higher speeds --> tiny buffers that pretty much need h/w flow control for anything above 56K. And the empegs, and most embedded platforms I work with, do not implement RTS/CTS h/w flow control.
So, I eventually plunked down CAD$30 for one from "The Source by Circuit City" (the company formerly known as Radio Shack Canada). Bigger, bulkier than the $10 ones, and with a longer cable (I keep it permanently coiled up, don't need the length), and.. it manages 460800 bits/sec without any flow control, and without dropping characters.
Cool!
So the point is.. YMMV.