i think CNSD-300FM (2011) may have been the last official update for that series (includes your x910bt).

You can find "hybrid-4.001" method in hacks forum of F series.

Assuming you are in US you can find Q4 2011 maps, and combine with that update.

Besides updated maps, several users indicate their unit seems to be more responsive and starts up a bit quicker. There are no other significant UI updates. You can "customize" the feel/skin of the units. Several folks have mods int he F Hacks forum that change the appearance.