It'd be really very handy to be able to duplicate a space. Export/import only works on 1 space I think (it seems to have lots of integer ids in there so I dare not try exporting, twiddling things and reimporting).
What would be really nice would be a 'copy space' option where you can duplicate an entire space as a different name/key.
e.g. setting up projects at codehaus; it'd be good to use an existing space as a base, then copy the entire thing, then after that either export/import to search/replace, or just manually modify pages after that.