I am very happy with it, and have noticed no problems, which is pretty impressive because this is a nightly build, not even a Beta / RC. The CM9 team has done a fantastic job with this version, and stuck very close to the original ICS look and feel.
Things I am happy about:
The settings menu. The stock build just seems so crippled to me now, after seeing the CM9 settings. It is too expansive to screenshot, but still quite organized. You can tweak everything from display gamma settings, to the lock screen, to individual volumes, to kernel performance, to (my favorite!) the notification LED. Coming from the Incredible, which just had the orange and green notification LED, having an RGB LED that I can play with is great. I have a green blink for texts, slow red for Gmail, and fast light blue for missed calls.
The notification drawer. (I couldn't get a screenshot, because the drawer retracts before it is taken.) I really missed these widgets, and now have quick access buttons to toggle Wi-Fi, LTE (So happy about this one!), GPS, Silent/Vibrate/Loud, and Auto-Rotate. There are other buttons you can add, but these are the ones I wanted. Also, I tweaked the battery icon.
Customizable navigation buttons. I re-ordered the buttons at the bottom (to more closely match my Incredible, actually) and added the search button, which behaves the same way.
All of the familar 'root stuff' built right in. Superuser (of course), Wi-fi tethering, screenshot, etc.
Over I am quite pleased, and will probably keep using this on a day-to-day basis. This is the way Android was meant to be. Can't wait for an RC!
Additional note: Of course, this comes without the Google Apps, so you'll want to download that zip from goo.im/gapps.