You'll have seen our own Rafe's news story on the Belle Feature Pack 1 update for the Nokia 603, 700 and 701 a couple of days ago - also worth noting is Yash's screenshot tour of the new OS version, which picks out several extra interesting details, including the reworked way of handling pop-up messages.

From the piece:

There have been some changes in the Messages app as well. Incoming messages show up with Blue background now.

The music player now supports Dolby Mobile 3.0 with Dolby Headphone support.

Pop Up notifications have been moved to the top of the screen in the form of toast notifications. No more annoying in your face pop ups!