Ah, thanks. I think that big concern for the M may be lag in its responsiveness. Otherwise, if they can address that, I expect that the UI will be great.
The DX50 UI is meh so I won't expect much more from the DX90. On the other hand, if they port Rockbox to the DX90, that is hard to beat.
As for function, everyone has their own needs. I don't give as ram's damn about a digital out but it is very important for some people on here. On the other hand, a good active playlist is top of my key function list. It is the big thing that is missing on my X5 and a reason that I may yet get the M. The X5 + Pico Power is sounding very good.
How will the M sound with IEMs and no external amp? Inquiring minds want to know...!
We both share the same feelings except for the playlists, I used playlists quite a bit in my iPod days but I tend to create directory favorites which work just fine for me. So playlist is not a must have but I have to say that if the M does it very well, that might change. :) I do have a little concern about the responsiveness however I don't think it is any worse than when I click on the play/stop or forward/backward buttons on my DX50.