I think you can avoid the whole update / re-install apps issue with the final if you are using the preview in a NON VM.
1) Backup / image your current OS + apps (this should be on its own partition anyway - separate from your data -- and don't forget the small system partition if it exists as well). You should always backup ypur OS regularly anyway so if you don't this is a good time to start.
2) Install and test the preview.
3) When Final comes out - restore your OLD image from your backup -- again don't forget the small system partition which should be the "Active" one.
4) Now simply Update to the final 8.1.
Use a program like Free Macrium for the backup - or a more robust commercial program like Acronis.