I've caught a couple of episodes, they're pretty damn good. Also, the last 10-15 mins of them are a mini-making of bit about the episode about how they managed to capture the images which is really interesting.
If the Planet Earth Bluray is anything to go by, Human Planet with be freaking awesome, and seeing Planet Earth on Bluray was what actually made up my mind to get a bluray player and HD TV. I would say that the Planet Earth blurays are the 2nd best quality ones I have seen, only Baraka beats it, and then only just.
I'm actually just about to order Human Planet, Earth - The Box Set (Earth: Power Of The Planet and How Earth Made Us in one boxset), Secrets of the Solar System (Brian Cox FTW!) and pre-order Secrets of the Universe (don't care that I haven't even seen the first episode, I expect it to be epic!) from Amazon