Hi,
I used Trantor 4.3 and migrated to nanoboot with DSM 5 without losing any data on last week.
I only replaced USB stick with nanoboot, booted my NAS, selected Upgrade into bootlist then applied pat file through Synology Assistant. I only had to reinstall app with package center, reapply privileges to shared folders and recreate my backup tasks. I kept all my data, including Plex db.
Aegys