I just got about to installing a third party ICS/android 4.0 rom on my Nexus S. I am so impressed by the amount of polish that has gone into this release. If you're feeling adventurous, the roms are hosted on XDA developers. Couple other phones have ICS roms being worked on too, so check it out regardless.
The HTC DHD rom is still in beta, no camera right now :c. Cant wait for them to release ics!
Installed ICS on my HTC DHD yesterday. Pretty cool so far, a few issues, the sound from the ear piece is kinda crap and the camera crashes.