I've been using one of these for a year or so, a brilliant bit of gear in my opinion.
The inbuilt condenser mics are pretty good actually, but of course a separate mic may be preferable depending on your needs.
I've multitracked guitar, bass and vocals on it often and it really sounds good. Easy to monitor the tracks with headphones as you lay another one down.
The reverb does help to fill the sound out a bit, especially on vocals. Although I do use it a bit on instruments too sometimes.
Mixing down takes a short while to get the hang of to be honest (will it did for me), and then having to export tracks to the export partition on the memory card takes a bit of time sometimes - but it is worth it actually.
Its small, runs on AAs if necessary, light, and works just as a portable multi-track recorder should.
I've also used it standalone using the inbuilt condenser mics to record some rehearsals. Not ideal, but surprisingly good. I tend to grab the individual tracks off the unit and mix them on my PC, adding some compression to keep things under control, rather than mix down on the unit itself.
Cheers
Geoff