A few days ago, Koush released his newly-updated Superuser app into the Play Store. At the time, he noted that it would be integrated into CyanogenMod nightlies in upcoming builds. As of the latest releases, the app is now the go-to for Su access on your device – but there's a kicker: if you go looking for it, you won't find it in the app tray.
You see, CM decided to literally integrate the app into the system, so you'll actually find it in the Settings > Superuser section. Of course, this doesn't affect the app's functionality in any way, and you can still use another Su app if you so choose.
Still, if you've gone looking for the Superuser app, now you know where it went.