Actually, I havn't bought them yet. My only concern with the Optipac is that it won't be long before the serial ports on motherboards go the way of the dodo and the ISA slots (from what I understand, by the end of the year, boards will be sold without them).
But the more and more I look into this (including a few emails to Andy concerning a USB model of the OptiPac and the problems involved with such a beast because Microsoft can't seem to do anything consistant), I'm thinking about buying one of his OptiPacs regardless (hey, there's always PCI dual serial port cards!)
Plus, Oscar now has their Pro spinner, which I think is really really keen, but they have no plans on making a USB model of it.