They've just recently released youtubekids.com and I've setup my daughters profile on there. Much easier to control the shows on there and things available, which is good.Like someone else mentioned you have to sift through loads of rubbish to find genuine good stuff. Some of the stuff my daughter watches I just cannot fathom and these girls makes 1 million views in days per video or pure rubbish!
There can be a lot of rubbish, but the more you use it, the more I found my suggestions match what I watch. So I watch anything from travel, to how to stuff, to the hot ones, to car rebuilds and general car stuff. I have a huge variety of subscriptions, but then they're all in one place.