So far, all revisions of MM5 are installed portable, so you can carry over all of your settings and library by copying the 'portable' folder to the new installation directory. This way you keep your old installation while having the same settings and data in the new one. I'm doing this for about half a year now, and so far it worked without problems.

So I like keeping up with the latest test builds, and up until now, I'd install the new build in the old directory, but I've realized it's better to isolate for testing. However, there's no way to import settings from a previous MM5 installation. I personally think that would be really useful.