I've heard of driver problems with the edirols. Crashes, reinstalls if you knock it off while the computers on, that sort of thing. Good hardware though.
If youre on vista emu drivers werent optimised last I checked either, but the dacs and pres are better IMO (than the Mbox at any rate).
Any of those 3 are basically the top choices though in that price range. Learning to use the gear right, or well, is a FAR bigger bottleneck to getting good sound than the gear, you should be fine with any of them.
Personally, though, FWIW, I think the software package and DACs and Pres of the Emus put them head and shoulders above, but have heard complaints about vista performance (have used 1616M with vista extensively and not experienced this) and the gain dials are a bit sensitive (occasionally irksome but nothing that cant be dealt with). Edirol hardware is good stuff, but software wise not so much, and mboxes are OK but I think have the poorest price/performance ratio because getting in the protools clan is a selling point with them.