So far I notice a slight bass roll off, technically it has good treble detail but lacks that amazing bass texture of Calyx M. Sound wise it has more similarity to the the new A series walkman. To my ears both the current A series walkman (and so far the xDuoo X3) are sound-wise below the ipod Nano 7G.
Lineout to my ear isn't good. Gapless does not work, even with the cuesheet playback.
It has an easy blind navigation which is good, this is why i bought it. Cue sheet works nicely. It compiles them all under a dedicated folder and you can browse using that instead of your folder.
dsf files plays but dst has issues, some play some don't. 24/192 files play just find, no issue.
Dual 128 microSD works no issue but I think anything more than 64 GB would be torture to navigate.
Soundwise it is as good as A16 but with a much more primitive UI, however what makes A16 a winner is its features which why I kept it, I use to feed for feeding my sony soundbar. Features that is not useful for portable usage.
Please bare in mind this is my early preview, my ears need a bit of rest, so does my body (sort of unwell) but I didn't want to leave you guys in dark.
I feel it is a good alternative to the sansa clip+ but I recommend it only if you can get it under 110 USD. Some other user of both X2 and X3 feels X3 is not sonically on the same lever as X2.