I'll take a stab at this one -- I think in the past couple months there has been some gravitation towards jEmplode primarily because you guys have been busy on other things and I've had freetime to continue development.
I can tell you the top three requests I have had for jEmplode have been 1) soup-on-empeg support, 2) download w/ tag rewriting, and 3) keeping pc and empeg in sync. #1 and #2 we've pretty much got, though i think #1 is at the wrong level (it would be nice if the Empeg just did this for us), but it's passable. #2 is thanks mostly to Daniel and his work on his ID3 parser/writer. #3 is still not there because it's just kind of a hard problem.
I think ideally that Windows folks _should_ prefer Emplode -- if we were feature matched, Emplode would always win because it has the native edge. I always think it's cool when Windows folks choose it, but I think jEmplode's place is on non-win32 platforms... I'll obviously try to keep the arms race going, though
Another popular (and easy to add) feature that I think tony mentioned was templated download filenames (i.e. {title}-{tracknr:2}-{artist}.mp3).
Mike