Ran 6.6 in my 898 and 798 and the biggest complaint I have is with waypoints.
#1 A huge portion of my waypoints icons changed to a different icon. This is on the 898. The same chip/points are fine in the Humminbird PC program as far as icons.
#2 You can no longer select multiple and change the icon for a select group of waypoints. I use the crap out of that and there is no reason whatsoever for that option to go away. Silly! Bring it BACK.