The import feature on wordpress.com correctly imports attached media, but does not resolve the urls in the posts. The urls in the posts remain pointing to the media on the originating (exported) site. I've tried this both with export files that I've created and with export files created on wordpress.com.
The problem does not exist using the importer on a wordpress installation (wp version 3.5.2) using importer (0.6.1). This importer correctly copies the attached media and resolves the urls as it should.
This is a serious problem for us as we are building an exporter from a third-party service and anticipate that a substantial number of users will want to move their blogs to wordpress.com.
I would be happy to provide export files for testing.
The blog I need help with is scd8418importtest.wordpress.com.