There is No Official ChangeLog yet.
here is a changelog for the changes till now, thanks to members of other form to report this
+ Upgrade CPU performance Enhanced touch screen - Very fast
+ Improve wifi, connection error OVI
+ Rotate Enhanced
+ V52 pictures and movies better!
+ Ovi Maps 3.04
+ Added more space between alpha and bottom bar in full keyboard
+ theme effect with turbo manifest
+ RDS bug fix after got problem in v40
+ Quick office 6.2.524
+ Kinetic Scrolling improve in menu and gallery
- Ovi Store 1.05(611) still out-of-date
Thank if it helps