You're bad feeling may very well be warranted. I contacted Tascam customer support and this is the email response I received:
"We do not have Windows 7 compatible drivers at the moment. We are working on Windows 7 drivers for all of our current audio interfaces, they will be available for download on our website very soon. This product is discontinued so there might not be a Windows 7 driver being developed."
Hopefully they'll release a driver, but it doesn't sound promising. I'd really prefer not to have to operate two different machines.
Apparently alot of Vista drivers will work with Windows 7, so the Vista ones Tascam released may work. My roomie is getting a new machine with Windows 7 next week, so I'll try plugging it in and use the Vista drivers and see.
please let us know how this worked out, i have to be able to use my Tascam US-428 and this driver in question is the only thing holding me back from upgrading to Windows 7 immediately.