There aren't many great YouTube alternatives out there for the iPad. Most of the ones in the AppStore are actually worse than the standard YouTube app you get with the iPad.
Nowbox is a YouTube alternative which transforms your YouTube experience into kind of TV Guide.
When you first boot up the app, you will obviously have to sign in with your YouTube account but you can also sign in with Twitter and Facebook. The reason for this is so that the app can also pull videos from those social networks and puts it into the app, a kind of hub for your videos from your friends.
Once signed in you can choose multiple categories which you are interested in and the app will get videos from those categories, curating them together.
As you can see, the streams are below the player. You can scroll across or up and down. I'm a film fanatic so I have VISO trailers YouTube channel as my first stream, enabling me to keep up with the latest trailers. Anyone seen the first Expendables? Crap story line but it's great to see the biggest players make a movie together. Anyway I'm going off-topic.
When you hit the little TV icon, by the gear icon, you go into Channel Management. From which you can look at your subscribed channels and social channels.
You can also browse other categories. Unbelievably I went for the Tech category. Under there you can check some of the most popular Tech related channels on YouTube. It's a great way to find new channels as well.
Not to forget you will be able to sync all your favourites and "Watch Later Videos".
Nowbox I think is the best YouTube alternative for the iPad. It makes the YouTube experience a lot more engaging because you're presented with content nearly all the time, you don't have to keep looking for it. It's also great looking, unlike many other YouTube apps out there.