I could find these changelogs
Changes made from version 4.60 to 4.70:
* Added support for one traffic provider
* Improved Points of Interest searching
Changes made from version 4.50 to 4.60:
* Fixed issue where some movie theatres were not being displayed through MSN.
* Fixed issue with system restore on non-Bluetooth units.
Changes made from version 4.40 to 4.50:
* Improve handling of the situation where overlapping map data is present on the device.
* Fixed issue where fleet management interface messages can get stuck in the outbox.
New firmwares since jan 2010 have .gma protection ,I donnow when this 4.9 has been released, anyway there are unlockers.