Well you asked for views from VF80 owners - I don't know anything about the Tascam.
Eric's comments seem pretty spot on to me. The VF80 will only record 2 tracks at a time, and transfer to the PC is slow (digital) or relatively expensive (CD writer).
However I love mine to bits and wouldn't swap it, and it is all down to how it is used. We are working our band up, writing, arranging and practicing new songs, and the sheer ease of use of the Fostex, and the amount of stuff we can dump on it, makes it perfect. It's also very robust and gives me a great deal of confidence. People who know better than me have testified on this board to the high quality of Fostex components - I don't know how that compares to Tascam.
Transferring to PC, unlike the MR8, is a pain, but I do it rarely enough that in the scheme of things it doesn't matter.
It's 16 not 24 bit, but certainly at my level I just don't think that matters a bit; I don't think it would to anybody looking in this kind of price range.
In summary, if you are a solo artist sitting next to a computer the VF80 is not the best choice, but if you are working with many musicians and want to record stuff fast, and edit it later, its the business.
Hope that helps
Garry