The official update notes on iTunes lists the following changes:
- Optimized for iPad and iPhone 5
- Stream videos with AirPlay
- Tap logo to open your Guide of channels
- Add and remove videos from your playlists
- Clickable links in video descriptions
- Improved accessibility with VoiceOver
The iPad app looks really good. I have never used the iPhone version because there was no point viewing videos on the older screen size when I could use the YouTube website in Safari or the free Jasmine app.
This app is definitely (and obviously) better than the YouTube app in iOS 5 and below, which was maintained by Apple. The UI is quite similar to the iPhone app. The pane that is uncovered by sliding the main screen to the right is always present in the iPad version. You can switch your main home screen to make it display uploads only instead of highlights from the channels you follow. There is also a voice search feature that can be used by tapping the microphone icon near the search bar. You can like/dislike/comment on videos and subscribe to channels.
However, I still don't see some essential features. There is no support for annotations on videos. You cannot seem to be able to select video quality. This is handy for users with low bandwidth or data caps. You can select between HQ on/off on the YouTube website and you can set your preferred video quality in Jasmine.
I also haven't seen any video ads in the app yet.
If you are on the first-gen iPad and still running iOS 5 as a result, you can disable and hide the old YouTube app as shown here and enjoy the new app.