This is great news. In 5 years I can’t remember a single time I’ve used the YouTube app other when I get redirected to it from a link somewhere else. Apple dropping it from iOS 6 means there’ll be one less system app in my folder of apps that I can’t delete.
Update: Several clever folks have pointed out what I never realized: by disabling the YouTube app in Settings → General → Restrictions, the app icon will be removed and any links to YouTube you come across in Safari or Twitter or email will send you to the YouTube site in Safari.