The Maps and Flash has been updated but Maps 3.0 is still not supported neither is Ovi support integrated into the device. Since the E90 does not support UDP(User Data Preservation), you need to take a backup of the device and the update it and restore it to get your data back.
Those of you have updated your E90, do share with us here if you find any other changes, as a V300 to V400 firmware update should have some significant changes