The Nokia 5800 has got a new firmware update to version 51.0.006 which is expected to improve the overall performance of this phone. The Mail for Exchange support has been improved in the email client. The Browser has also got some improvment. Video Calls also might work better than usual.
We could only find this much from the official changelog but you are always welcome to share what changes you saw with this firmware update.
Make sure you take a backup before proceeding with the update
Thanks Amit !