2 - if google hadn't changed the look everyone would have complained ICS was the same as GB, even if all the real changes were under-the-hood.
Changes like ICS is not very healthy for the platform and should be avoided if possible, Chrome running only on ICS is prove of that
I think real goal of ICS UI changes is unification, bring identity in to it, in similar way to iOS.... or WM7, J2ME, Windows, GTK, Qt (not sure about sybian or BlackBrry i don't follow those)
Normally Android was do as you like platform (by that i mean it didn't even bring common UI stracture, other then menu button API), that resulted on inconstant UI practices, some app didn't even change after bringing them from iOS
Now ICS bring common UI structure things like action bar and tab element.
But you want to know real real reason behind ICS? Is to bring Honeycomb to smaller devices, having 2 different systems that run same applications is not healthy either