I've read that the Nokia N9 also does a good job of running ICS.
Other counter examples: Boot2Gecko (runs well & generally demoed on a Samsung Galaxy S2), Ubuntu for Android, ASUS Transformers running various Linux distributions, ...
Because the touchpad had a fairly open bootloader and we built a more versatile one for it based on the same code base (moboot). The bootloader in the OMAP chip also allows booting from usb and does not require the second stage be signed.
Other counter examples: Boot2Gecko (runs well & generally demoed on a Samsung Galaxy S2), Ubuntu for Android, ASUS Transformers running various Linux distributions, ...