Here is the most current OS for the 8310.
http://www.blackberryforums.com/gene...eastasian.html
I would use DM 4.7 w/o Roxio Media Manager.
If you're not having any issues with your current OS, there's no need to upgrade unless you want the features in 4.5. HTML email, Docs to Go, voice/video recording, youtube are some features in this release.