I love Sirius! He is my absolute favourite HP character, followed by Ron and then Lupin, then Neville. And they're all here...they're all great and they all get an amazing role.
I love the complexity of the story and wish I had a time turner of my own. I think everyone would love the chance to go back and make changes to events in their past, even knowing that it could change their future.
What I really love about this book, is the way that Ron sticks by Harry no matter what. Their friendship is the epitome of a Bro-mance, and it's one of the most well done male best friend relationships I've read.
I also love that no matter what happens, no matter what book you're on, the relationship between Ron and Hermione just gets better and better. And you know, without a doubt, that they're meant to be together.