Messy Movie Manager, there's also a another one or two java based ones which could work.
XWMM can work, it's a web browser based interface to XBMC's own media manager. If it doesn't work via the repository install then you can get it going by using the mentioned method 2 install and place the folder in
Yeah it's a shame that there isn't a decent Media Manager along the lines of Ember for the Mac yet. It's one of the two things that keep me with Plex, that and the easy sharing of libraries (complete with artwork) between machines/iOS devices.
I almost switched completely to XBMC when the ATV2 client was released, but having to store a copy of the thumbnails on every machine with no EASY way to share them sent me back to Plex.
Although I do maintain my XBMC library "just in case" lol. XBMC is way to cool to forget about