I have been able to successfully start MediaBox SVN version on Mer 0.12. The UI works quite well, but animations don't look as fluent as on Diablo. Also the Nokia Sans Cn font is missing, of course, so the fonts are a bit different.
Browsing the file system and UPnP shares worked fine. With libxine, I think, we're not far away from audio and video when Mer will have audio.