http://www.lowrance.com/en/Downloads/Product-Software-Updates/HDS-Software-Update/

What changes are made in this update?

HDS 4.1 includes many new features including:

Sonar Performance – Improvements include better bottom tracking at high speeds, enhanced deep water depth tracking (greater than 1,000 feet), and shortened lock on time for trolling motor mounted transducers.

Charting Enhancements – Quick access mapping selection is now available with Lowrance/Navionics chart toggle under Chart Options or soft key accessible on HDS-8 and HDS-10. Also, users can now display points of interest supplied by the Navionics User Community.

Fixes– Updates include accurate distance measurement between vessel and active cursor as vessel moves, correct altitude overlay for altitudes greater than 9,999 feet, and EP-60R fuel flow sensor corrections.

I just updated my hds 8s. I was amazed at how fast it did it on the units. I also expected to have to change my settings back but with the keys still being quiet, the soft keys still the same and the screens coming up like I left them I guess that info was not redone thank goodness.