Advice: Best way to batch import users INCLUDING extended profile data?

I'm migrating an existing site to Buddypress, and I need to import a few thousand user accounts. I have all the data I need in CSV, and basic user creation isn't necessarily a problem.

But all the plugins I've come across (at least the reliable ones, including the WPMUdev ones) only seem to handle standard profile data -- I have a fair amount of extended profile info and it would be a shame to lose it.

Any ideas?