I have a BU-353 too and it is awesome. And yes it is SIRFIII.
The pharos 360/560 are pretty good too. (SIRFII/SIRFIII and the 360 glows blue

)
All USB is serial... so yes it is serial. Never had a problem from resume. Although from what I have seen around here half the time if you have resume issues it is the motherboard. Other time it is the device. So it will fix it if you are lucky, but it wont neccessarily work.