Once they introduced transactional logging (highly recommended for busy systems) there were a few more steps to the migration, but they are all well documented and surprisingly resilient.

I managed to migrate a few TB of email from a dying server and it handled mid migration crashes surprisingly well!

I think the domino stack was getting better while the notes client was losing the plot. Most people where I used to work were happiest with mobile clients connected via exchange active sync to the domino servers.