The standalone YouTube client, released mid October after the inbuilt one was pulled from iOS6 has been updated to support the larger display of the iPhone5 and optimised for the larger screen of the iPad.
The new version optimised for the iPad is much better, giving you a constant view of your subscriptions, and when playing a video the client defaults to a 3/4 view with info about the video below, and an option to switch view to the comments, all while still watching the video. If you want to view the video full screen, simply press the expand icon.
The iPhone5 update brings no real changes other than full use of the taller 4” display.
>> Download the YouTube App from the iTunes Store here.