@TGOM, good report on the other aspects of the AK100. Whilst I'm not saying what you're reported is incorrect, I'd just like to state it depends on where you're coming from.
Judging by your thoughts there, you better stay away from the DX100 and the HM-901 :D. The DX100 backing is a thin sheet of aluminium and nothing really to enforce it - so it dents. The DX100 UI is slow, and even after booting up you'll have to wait a few good minutes for Media Scanner to re-index. I leave my DX100 on, so I don't have to worry about the Media Scanner (unless I add/delete songs, or eject and insert the microSD) - the DX100 is $829. As for the HM-901, fair enough the one I played with was an October prototype - and it was plasticky. Didn't reflect a $1000 device (or $1200 in Japan - with no amp).
Seems all these high end players (maybe the Tera Player is the only exception - there's no LCD to shatter), have build issues.
The iDevices, Sonys, and Cowons seem to be better built. Whilst the Sony NW-Z (don't know about the NW-F's) skins do peel after time, at least they're only $400 devices.
Actually of all the devices I've owned I hate to say it but it's the iDevices that's the most consistent, dependable, and durable for use. I've not had any problems with album artwork, synchronisation is mostly clockwork and think-free with iTunes, and they're pretty durable. I still have my old iPod Photo after 7 years?
In terms of durability my Studio V 3rd ANV is it. Not even the iphone4 or any ipod or Sony for that matter will compare in that area. Of course in UI it loses out but in terms of durability & sound quality, not even close.