I finally got the ICS update yesterday (Koodo/NexusS). I've been looking forward to it since I've been reading all kinds of great things about it. I'm not disappointed, but I'm not totally blown away, either. I was hoping for a radical improvement, but so far it seems to be more about aesthetics than functionality. The data tracker is nice, but I had a pretty good ap for that already (My Data Manager), in GB. The camera functions are a definite improvement, and it's a lot faster to find something in the ap drawer (although I prefer the appearance of the rolling scroll in GB). Oh, and the new "Roboto" font is very nice. One really big improvement in functionality is the ability to see which aps are open by long-pressing the home button (as well as closing them by swiping to the side), the same feature that's in Honeycomb on my tablet.
I definitely like the multi-coloured, electronic "X" graphic on the GB start-up screen better than this new weirdness in ICS, but I almost never restart my phone anyways so that's a minor gripe.
Generally speaking, I like the new os, but I liked the old one, too. So far I'm not sure which one I like better.