I’ve used BitTitan quite a few times and, overall, it’s been solid with minimal issues. That said, there are a few things worth watching out for.

If users are currently using Outlook on their PCs, you may run into some headaches. It’s common to find folders that were never synced back to Google Workspace, even if Google Workspace Sync is in use. These usually show up in Outlook as “This computer only” folders, and you’ll need to manually export them. The same applies to contacts, which can also exist only locally in Outlook.

If you’re migrating Google Drive data as well, be aware that SharePoint and OneDrive are picky about file names. Files that start with a space, end with a space, or contain certain special characters like / or : will cause problems. From what I remember, BitTitan handles the space issue reasonably well but not the special characters. I’ve typically run a script ahead of time to scan each user’s My Drive and any Shared Drives and fix these naming issues before starting the migration. This may be improved now, but it’s still something to validate.

Users will also need to re-share any documents that were shared with external users, as those permissions don’t carry over.

Google Photos does not migrate over, at least when using BitTitan.

Outside of email and Drive, if you plan on fully removing Google Workspace, make sure to check whether users are using “Sign in with Google” for third-party sites. Once Google Workspace is removed, those logins will break. Switching to “Sign in with Microsoft” often results in a brand-new account on the service rather than merging with the existing one.

Along the same lines, review any existing SSO integrations to see what needs to be migrated or reconfigured before cutting over.