I've been playing with the various versions of Metasploit on my (new to me) N900. Here's what I've found to work and not:

Metasploit Framework 3.6:
Last version with sqlite3 DB support, so db_autopwn works with this version and the N900. There is a ruby sqlite3 deb available on the forums that works (just needs to be moved into the proper directory). I don't believe that there is a working postgres or mysql for the N900?

Metasploit Framework 4.5:
Completely unworkable... freeze the device and usually causes a reboot.

Metasploit Framework 4.4:
Works (pretty slow to load), but search is very slow and complains about db missing or cache not being built. Without search this is sort of hard to use. Not sure if there is a way to fix this issue.

Metasploit Framework 4.3:
Works very well, not too slow to load, search works properly.

Updating:
Newer versions you can update with git (avoids the svn 1.7 required problem), but there isn't much point as 4.5 is unusable. Older version you can update still with svn, but if you do a svn update, it gets you to version 4.5. I suppose you could update to a specific revision to maximise the benefit of updated exploits while still avoiding the problems above. I'm not sure what that revision number would be however... that requires more research and testing.

Personally, I think I will keep 3.6 and 4.3 on my device. 3.6 for autopwn and 4.3 for updated exploits/payloads and the search capability. Maybe 4.4 for those times I may require it, but I'll have to find the exploits/payload some other way (web?)