This was the first episode I was REALLY interested in. First off, I love angels (stone or not), and these angels grabbed my attention. They also were the first thing to scare me in a long while. The concept of the angels was brilliantly thought of and excellently executed. As a story writer, this was very solid and amazingly written.
Secondly, the Doctor and River appear in a weird order. Her past, his future. That is very confusing. Some times you have to go back and watch episodes out of order just to understand what is going on between them. Although, it is quite amazing to think of having that kind of relationship. I’m glad it’s River and the Doctor. I cannot see either of them with someone else.