I really like these recorders and use two of them for simple dubbing which is not really what they are designed for. Nevertheless I find them physically easier to operate for a guitar player than any fiddly multi-tracker or looper I've ever used. Also the higher resolutions capture acoustic arpeggios/fingerstyle playing which I find lower resolutions struggle with. The menu is as simple as it gets, for my purposes I just set it and forget it and it remains a go-to functional piece of kit.
Beware that (as far as I can tell) neither the USB memory playback or the cascade multitrack function allow dubbing-capable multi-tracking. The cascade function allows multi-tracking akin to what you get with a field recorder. I get around this by playing one recorder back into two mixer tracks while recording to the other recorder.
For listening back only, I find the headphone outs on the DA3000s sound better than monitoring through the mixer.
One thing to bear in mind when planning to install these in a rack or rack case, you need to leave space for ventilation.
For guitar players who don't have a sound assistant on hand to help them out, a simple to use high-resolution rack recorder is a good way to go. I would have preferred the front panel to have been less pretty and more rugged looking.