We saw the camera monster Nokia PureView 808 running a newer Symbian Belle iteration named the Nokia Belle Feature Pack 1 which was quite a substantial improvement over Belle and Nokia is now rolling out the Belle FP1 as an update to recent Belle devices like Nokia 701, 700 and 603.
The most notifiable change is the bump in processor clock speed, it was speculated that the 603 would not get the bump in speed but it seems now 603 too is getting it. The update also brings major improvements in performance and also to the interface. The update also brings with it Microsoft Apps and Nokia Maps Suite 2.0. Most important changes the update brings:
Source : All About Symbian