I know that feeling ... we'll have to shut down our board for two DAYS , because the importer isn't capable of incremental importing.
Our import lasted 6 hours longer then the import in the test installation with an older importer version.
FYI new migrated forum is up and running great
(to clarify, this was not the same parent_node_id undefined problem as mentioned before.. that part was fine in our install)
Grats. Were live too and shockingly our users didnt complain much.
Its still a bit disappointing that nobody seems to care about all the problems here in this thread.