I own the previous incarnation - the M90 - and it hasn't seen the light of day in a year. I don't know if the M92 is a significant upgrade, but the M90 was very problematic for me. If I let it sleep - vs. shutting it off - it wouldn't turn on. I'd be reading and it would jump back to the home screen. There were other niggling problems as well.
I vastly prefer my DX, and use it every day in conjunction with my PW.