Google denied Android 4.0.1 Ice Cream Sandwich upgrade on old Nexus One officially. But that does not stop developers from create Android 4.0 ICS ROM for Nexus One. And ported to HTC HD2. Since the porting is just started few days after Google released Android 4.0.1 Ice Cream Sandwich source code to Android Open Source Project (AOSP), it is consider beta version to me as not all the functions are working well and smoothly. But it sure looks good for early build and no soft buttons like Galaxy Nexus. So you have extra space on screen and use hardware buttons instead. And I am looking forward for the main stuff that I want in Android 4.0 to be working ~ 2D hardware acceleration with GPU.