I think I may be suffering from this bug. I'm trying to export users from a 1.5 site and update them (all already exist) in a 2.5 site. For both exporting and importing I am using 2.0.6
However, I am still getting the 'Invalid user type ... Super Administrator' error on import. Weird thing is, this only occurs with super administrators, other user type (author, administrator, ...) work fine.
Edit: I found the issue, it wasn't this bug after all: apparently someone changed the name of the group in the 2.5 site from 'Super admininistrator' to 'Super administrators' (notice the extra s). This (naturally) made those users faikl in the import. A simple group rename was all that was needed.