I’ve finally migrated my email from google apps to outlook.com. The key item that caused some issues was using domains.live.com. I had added the MX record that proved I owned it (and email was flowing correctly).
However, it was always set to “pending” and never switched to “active”. The problem is that the Hotmail.com MX record is the only MX record you can have. I had some of the old gmail records listed still, but at a much lower priority (higher number). Removing them immediately made it switch to active.