Occasionally you can get an update that will cause more harm than good. Just before my first trip to Boston, I updated my SPIII firmware. When I got to Boston, the Find Address function was not working. Much later, I figure it as a firmware conflict with the City Navigator software only - confusing as heck at the time.
Long story short, once you do the firmware update, check that your unit still performs as expected. If not, try reinstalling the new update or install an older update. If you don't have an older update, ask here at the forums. Someone should be able to help. As a mater of routine, be prepared to reload your waypoints, maps or reset favorite features.
I have never had another problem like Boston. Many of the Garmin updates have added features to my old units that I value highly.
If you are the cautious type, wait for the forums to comment on the various updates.