Just recently, eMusic updated their download manager to one based on XULRunner, to the outcries of many people on the forums. So I took the work I did for Naxos a while back, and built Windows and Mac OSX versions of my formerly-Linux-only eMusic/J download manager. I’ve had feedback on the Windows version saying that it’s working great for people, which is good. I don’t have a Windows or Mac machine to test either of them on, so I wasn’t terribly confident.
Anyway, they can be found here: Windows version Mac version
(Update: try the eMusic/J homepage for the latest version on all platforms.)