That is awesome! I used KDP to self-publish a couple of paperback non-fiction books a few years ago. Back then they didn't have the ability to make interior color pages. It is pretty amazing how far publishing tech has come with print on demand services.
Yep the quality on the inner pages are very good. Kdp does not offer much options for the cover thought. I would have loved to try a glossy effect on the title. I guess that's not really possible with print on demand...