I've had this unit for about four months. As an audio interface for recording it has worked fine. Presumably these things are supposed to function as a "sound card", and that's mostly true (otherwise Tascam wouldn't provide step by step instructions on how to set up audio to play iTunes through it!)
I'm using a Mac, and I have noticed one annoying tendency for the interface to disappear after the Mac has been in sleep mode, and I'm still not sure if this is an issue with the interface itself, the drivers, or the OS. I can usually reconnect it by switching the 1800 off and then back on again. However, I was playing a series of video clips in QuickTime the other day, and after about the third or fourth clip the interface disconnected and fell off the device list completely. Only rebooting the computer would restore the interface. This is weird. Again, I can't tell what's causing this behavior, or whether it's in any way related to the sleep mode issue. In any event, so long as I have it running for recording purposes it seems to be fine. I think assuming that it is a substitute for a soundcard is assuming too much, although I would prefer not to have to keep switching back and forth.