I don't know if Roland has significantly improved their preamps or what . . . but I've recorded a lot with a VS880 and
a Boss BR8, and I'd have to say the preamps are one of it's weakest links. Not bad for a few tracks, but as you start piling on the layers, the overall mix takes on sort of a thin sound; something I associate very much with a homemade demo.
The other somewhat weak links would have to be the a/d conversion, and the compression. As far as the effects go, I think they're pretty damn good. The reverbs, choruses, flanges and other fun stuff are all about as good as you're going to be able to get for the money -- and damn near as good as the really expensive stuff.
When using an outboard pre, I've heard noticeable improvement. Couple that with an outboard A/D converter and the results are even more noticeably better. So I would have to say a decent outboard preamp and a/d converter could work wonders.
Some suggestions:
* M-audio dmp3 + ART DIO
* dbx 386 preamp/converter
*
Joemeek twinQ
or my choice, the Mindprint D.I. Port
After that, I'd look at a good compressor. The Roland just doesn't do compression as good as outboard or DAW.