Just some rapid thoughts.

Music Finder now works with USB files.
Styles sound better than S900 because of added megabrass and megastrings. Some with same names reworked.
Screen looks great.
OS feels the same.
New voices like S.A. organs sound very realistic to me.
T3 styles load ok but many voices are missing. Many are probably mega voices and these are a pain in the behind to change if there is no corresponding mega voice in the S910. I would just go with the converted T3 styles that sound better than I thought.
A lot of great OTS's (One touch settings) that take advantage of the additional voices.
Old registrations work fine.

I'm happy I made the upgrade.

Beakybird