In my experience, the GB changes are mostly under-the-hood. And given how the roms are struggling to get it to run smoothly on the D1 I have to wonder what stock would be like.
Now Ice Cream has me excited as some of the cools features of Honeycomb should come to smartphones (scrolling widgets stock, updates to the notification bar, etc..). But we won't see Ice Cream until probably Q3, for roms...Q4 for VZW updates and maybe never if you have Samsung