Android has always been criticized for its not so smooth UI, and that’s because it was rendering all UI graphics with the CPU. That, of course, is crazy, and I believe it was a major design mistake implemented in Android from day one – or rather the lack of hardware acceleration for the UI was the mistake.
You shouldn’t have to run anything graphical on the CPU. It should all go to the GPU, because it’s an order of magnitude or two more efficient at handling graphic elements. So now that Android 4.0 has hardware acceleration, it should easily run the whole UI at a silky smooth 60 FPS (obviously capped), and it should be able to save a bit of more battery life, too.
It seems that Android 4.0 is really Android reborn, and they’ve thought about how to rebuild a lot of things from scratch, for maximum performance and for a more modern look. Honeycomb was the beginning of this work, but it wasn’t complete, and it worked only on tablets. Now Android 4.0 will work on both tablets and phones, and later on set top boxes, too.
One other feature of Android 4.0 related to this is that all apps being built with Android 4.0 in mind (API14) will have hardware acceleration enabled by default. In Honeycomb they didn’t want to break compatibility without the developer’s permission, so they left it to the developer to enable it in their apps. It’s only one line of code, though, so I’m sure it wasn’t too much of a problem, unless they really didn’t now they could do that.
I believe enabling it by default was the right decision, and once Android 4.0 arrives on millions of Android devices, we should start seeing a lot more polished Android apps that are also built with Android 4.0′s design style in mind.
Source: Android Developers Blog