Won't trust MS for any migration
Local University here attempted to move to BPOS before Office 365 existed, and were promised a migration path.
After about 8,000 users were migrated, it turns out the only MS supported migration path for over 16,000 users (faculty and staff only) was to sync to a PST and upload the PST to Office 365, one user at a time.
MS is quick to bring in migration tools for other's products, but once you pick an MS product your SOL even if you want to move to another MS product.
The University went with a local MS Exchange deployment, and had to do the user by user migration...
Personally having been a lotus user (and administrator, at times), I far prefer Notes and Domino over Exchange and Sharepoint.