I see an awful lot of people saying it offers no improvements. Personally, I think it does.
I keep my phone up to date as much as possible. When ICS was stable, I jumped right in. I haven't ran Gingerbread in a long, long time—but from what I remember, it had some lag. Android, in fact, was known for this lag. You couldn't read an iOS vs Android debate without this lag being mentioned (at least when Gingerbread was the newest). And I had tried everything: every lag fix, every tweak, every ROM, every kernel, governer, scheduler, OCing, UVing—I tried it all. But I still remember there being lag.
Now I'm in the present. I've been running ICS since it was stable and, quite frankly, I don't notice that lag. I mean, yes, my phone does still lag—if I'm doing something processor intensive in the background—but not like my memories of Gingerbread. Back then, it would lag scrolling through my list of apps; it would lag doing menial UI rendering without anything running in the background. That simply does not happen anymore. Not in my experiences. Not with ICS.
Granted, as I did in Gingbread, I do in ICS—I've applied every fix, every tweak, and every possible software combination that I could get my hands on. I've tried every ROM, every kernel, every setting imaginable. And I do this because I've been thoroughly impressed by the community here at XDA. This device of ours is over 2 years old now. But the software progression does not stop. We move forward as if the hardware was built just yesterday. And I have to tell you, our phone is keeping up—it really is. My phone is faster than a lot of my peers, even with some of them having much newer hardware. And I honestly don't feel I could have said any of this if I had stayed far behind with Gingerbread.
Everyone wants a new phone. It's newer, better, faster. But what they don't realize is that software can fulfill a majority of their wants. It is a continuous improvement, however gradual it may be. To not want to upgrade your software is like not wanting to upgrade your phone. And let's be honest, who doesn't want a new phone—one that's newer, better, and faster—without ever having to buy one.
I do. And that's why I update my phone. But maybe that's just me.