I agree that a USB connection would be good - but judging by reviews of machines that do have it (like the Tascam) it isn't particularly fast.
What I can tell you is that ADAT and SPDIF transfers are a nightmare, especially if you have more than 8 tracks. Using CD isn't quick, but it is straight forward for me because most of my songs fit on one disc.
The machines that have SCSI (VF16 & 160) can save to a SCSI hard drive, which can then be 'seen' by a PC (apparently the PC can be connected by a SCSI/USB adaptor - but I haven't tried it).
Orc