USB really isn't fast or reliable enough for decent video work. Anything converting analog to digital on USB can't be too powerful or take enough time to do a good job since there's a max power of 2.5 watts available to USB devices. The magic of dedicated chips is good, but not that good.
So to do any good at all, the USB converters either have to drop frames, use lower compression methods that result in too high a data rate for USB and/or sacrifce the sound quality.
A PCI bus card doesn't have this problem.
Fav quote - "Experience is whatcha don't get 'till ya don't need it no more."
System - Athlon 1.4GHz, Win98, Hauppauge PVR250 receiver and compressor.
Software -Magix Movie Edit Pro 10, Nero 6 + NeroVision Express, Moho 4.61, PSP 8.1, Bryce, Quicktime 6.52 pro, Goldwave 5, DVD-Lab.
Cameras - Panasonic GS9, Canon ES8400V, Canon EOS D20 and Canon A70