First off, the update should fix the notorious battery drain issue on Gear Sport and other units, which Samsung already tried to fix with a previous update to no avail. The interface to read out exercise information has been rearranged, and gotten easier to discern, plus you can now add a custom and personal heart rate target, too. The notification intervals while you jog, bike, swim, etc., can also be customized now.
Las but not least, besides the usual bug ironing and stability improvements, with the freshest R600XXU1ARC4 Tizen build you can finally disable that annoying alert sound that beeps every time you move after a prolonged inactivity period. Sweet. Don't fret that the release date is a couple of weeks back, these things take a while to roll out to every users, but you'll eventually get it.