I know whatcha mean. I think they need to include the ability to search for people and view their pages, to comment videos, and to login to your account so that instead of bookmarks you can just add them to your favorites on your account. My opinions, but I think they would up the use of it.
I know what you mean. It would be nice if you could have the app smart enough to have you logged in and able to leverage your existing YouTube account when viewing content. It's nice to pull from your list of favorites or to view shows in your selected channels. I would hope that's something that could be added into the current app. It currently seems weak without it. The mobile interface via Safari is fair enough, but nowhere near as functional as building in those capabilities into the app itself. Good luck on getting Apple or Google to make this happen though.