What Adobe does is to analyse the overlap of two pictures and choose which part should be taken from which picture. ICE could really need this kind of smart way of analysing contrasting objects to create the illusion of a seamless panorama. You notice
ICE failing when taking panorama pictures where people are walking by.
Bas, also try to see if your camera keeps its light and focus setting by keeping the button half-pressed between pictures. This will illiminate the need to adjust for light differences.
Here's one of my longest stitches to date, 34799 x 2020 Pixels (70.29 MPixels) :