Here's the changelog, from what we can unearth. Do please comment if you notice something else!
- SIM Lock 3.0 and B2B Certificate, phase 1 added
- Startup settings baseline updated (wk47, 2010) (new dates etc.)
- After a hard reset or on first use, Camera shortcut is replaced with Ovi Store shortcut in the Home screen
- Removal of Ovi Files (service is now outdated)
- Vlingo application removed
Anecdotally, some have found that Camera performance is better, especially the auto-focus.
(NB. The v54 rollout has been somewhat extended, but I held off reporting the story until our own Euro-sourced device had also received the update.)