Flashed the AOSP version of Ice Cream Sandwich to my Nexus One! No hardware acceleration yet, but at least it's faster and less frustrating than the emulator. ROM is available on XDA: http://forum.xda-developers.com/showthread.php?t=1348670 though it doesn't include the Google Apps. There's only 4MB free on /system, but pushing most of the Google Apps to /data/app instead seems to have worked well enough for me.