Perhaps from a developer's or architect's perspective, but I've heard very little that affects the end user in any specific way. Can you tell me, as a user, what specific features are going to be new and wonderful that I must have? Face recognition, cool. Not groundbreaking. Now from the standpoint of unification of devices and developer hooks, I'm there. But as a user, I expect little immediate impact. There will be a few new kewl tools. But I have yet to hear of really compelling advancements that I'll see on my current phone. As you say, the majority of it is under the hood. So for developers, it's significant. For users, not so much right now. Perhaps new app capabilities in the future. But they're not here yet for the most part, so most users will see only incremental changes. I think my phone will look pretty much the same tomorrow as it does today. The update will come when it comes. We'll see what developers do with it. Could be really good, but it's not tomorrow.
Android 2.3 Gingerbread vs. Android 4.0 Ice Cream Sandwich
A few additiona not mentioned in the above article that immediately come to mind: the ability to take screenshots, the option to freeze any app from running (including bloatware), ICS-only apps (such as the vastly improved Gmail), and Webtop 3.0.
And most of the under the hood changes are not just for developers. The changes represent noticeable technical differences that have an impact on how your phone actually performs:
Learn about the technical differences between Gingerbread and ICS
There's more to ICS than just the above, but that should be enough to show that it's far more than an incremental update.