With CyanogenMod 9, the CM team decided to go back to the drawing board, do some major code clean-up so that future Android releases won’t cause them too much of a headache. Due to this, CM9 was under development for quite a long time. ICS was pushed to AOSP sometime around mid-December, and the CM team started rolling out nightlies sometime around early-March for a bunch of devices.
The first RC was released sometime in June with the RC2 following it after a month. Now, nearly a month after the RC2 was released, and more than 6 months after nightly builds started rolling out, the CM team has silently released the final version of CM9. As of now, the final version is only available for the GSM variant of the Galaxy Nexus.
There has been no official announcement from the CM team about the release of final version of CM9, which should hopefully happen once the stable builds for other devices are available. Galaxy Nexus (GSM) owners can download the stable build of CM9 for their handset from here.
Now that the final build of CM9 has been released, official CM10 nightlies based on Jelly Bean are imminent.