You asked, you waited, and now we've delivered. Following decades of planning and thousands of pounds, along with help from experts in the audio processing community, we're now able to bring fading music to MCJukebox!
For music you haven't specified a fade duration for, and also regions, the duration used is the default fade duration - you can change this in your admin panel (it's set to not fade by default).
You can override this default using /jukebox music <ign> <url> <fadeDuration> - if you're a developer, the Media object now also has support for fades (use -1 if you want the default).
And finally, we've also made teleporting work with regions. You're welcome.