i was wondering that very same question. anybody out there have experience with them? how would they compare to other similar setups, like the onyx series from mackie? i'm a little hesitant. i feel like i should wait and save up to get a decent mic pre, like one of the avalons, and couple it with a straight forward computer interface. but the $$$$$.... i have a dbx 2-channel tube pre and gina24 right now and i'm happy with it, though more in channels would be nice.
i like that the tascam can be used as a control module for the software, which in and of itself is a huge plus. you could always get the tascam and add the 2-channel ART tube pre-amp (~ $500), which will give you at least two decent mic pre's in addition to what the tascam has. (i heard they are good quality, though i've never heard them myself.)