Sorry, but I couldnt give a flying shitee about the interface. Thats just wrapping paper. I care what they sound like. Its a music player for god sake.
All the ones I'ev heard sounded bollocks. I'll keep an ear out for the new ones. I may or may not revise my judgment 
It's not wrapping paper when you're taking journeys to and from school each day, listening to it between lessons, constantly changing band/song, the worse sound quality is nothing compared to the brilliant interface imo.
I've had MP3 players which sound amazing, with bad interface, like my old Iriver PMP, the thing was slow as $%&#, and took years to change song. The Ipod works flawlessly.
Well, horses for courses, but my sony vaio sounds great (for an MP3 player) and even though the interface was often slagged off on it (it was discontinued due to lack of interest because out of the box it didnt play MP3 or WMA; it converted to (the superior, in point of fact) ATRAC: it was no trouble to update the firmware, though :D), I dont find it a problem in the least. And thats with analagous situations: I dont go to school, but on the way to work, at my desk and so on (I used to use it for that stuff till I got a phone that can do it).
I had a creative zen before the sony: halfway house: sounded OK, no problem with the interface.
I mean, FFS, in this day and age you wouldnt think anyone would have trouble with some piddly menus and buttons: no matter what the interface is, you get used to it.
A mate of mine has an Iriver that sounds ok, and he's never complained about the interface once.
P.S. In my estimation if a music player doesnt sound good then it doesnt work flawlessly ;)