The above works fine for downloading from the maemo.org repositories but does it work from Ovi store too? I mean can aptitude get stuff from Ovi and not unpack it, especially paid-for s/w?

When you do a back-up with either Ovi suite or the build in back up tool, it stores a list of installed software (for better or for worse!). I think this is supposed to allow you to reinstall s/w, including paid-for items without paying again. You seem to have problems the Ovi servers, which might prevent the above working though.