Firstly, we all know that DS9 is awesome
Secondly, the flashback sequences are done really well. It reminds you of all the greatness they accomplished over seven years, and that this was a series that was definately character-based and developed them all into full realised and well put together (writing, acting, etc) characters. One of my favourite scenes from all of DS9, is when Kira steps up to Jake, puts her hand on his shoulder and they look out the viewport. No words needed to say so much (getting misty-eyed at the thought of it).
Thirdly, it is a shame Jadzia doesn't feature, as she had done so much (starting with finding the Wormhole). But I kind of like that it was just Ezri, as it shows how she has become more sure of herself, of who she is without relying on the past lives of others.
Fourthly, the relaunch books for DS9 are great. The characters are well written and act just as they would in the series, the combination of old and new helps give a new dynamic without taking any focus away from Kira, Bashir, Dax, Nog and Quark. Getting to see Kira in command is also a huge thrill as you know she would be brilliant as Station Commander. Another huge plus is the development of the Andorians, I love the four sex idea, it helps to make them truely alien. I have to admit though, that my reading of the series stalled at the Worlds of DS9, for some reason I haven't been able to get into them as much as the others, but need to try again.