I've had a Mitsumi CDRW USB drive packaged as a Pacific Digital 4x4x8 drive for some time now. It burns fine under OS 9.X, but not at all under OS X. Not under ANY version of OSX, from 10.0.1 to 10.2.4.
The X side does see the drive, and attempts to burn CDs, but always stops with some "Can't...