Okay, I've finally had time to re-read the first four issues and give this one a second pass. So how does it stack up?
Very well, actually.
Barry's solved his cold case. Zoom's not only ruthless, but petty and vindictive as well. The changes to the other characters work: breaking up the twin dynamic will simplify Wally's sidekicks, and it's good to see Iris take a step toward her destiny (though it'll take me a while to warm up to her using the Impulse identity).
The main thing I didn't like about this book is that it really feels like the story itself is less important than shifting characters around. I'm looking forward to reading a Flash story that's actually a story and not just setup for the real story.
Full review here.