I had the chance to watch the workprint myself tonight. If I may say so, I felt it worked remarkably well.
I did, however, feel like one thing was missing: Leia reporting that the weapon was about to be used, to explain the apparent urgency as the Resistance prepares to head to SKB. So, I went back and took another look at the briefing scene. I was able to pull something off that I feel solves this issue:
https://vimeo.com/171864217

You’ll notice that I am unable to have her identify the target. However, this may be a good thing, since it would help explain why she didn’t attempt to warn the Republic. We see Hux tell his side that they’re targeting the Senate, and we even saw he and Snoke decide on this. But, Leia appears to only know that they are preparing to fire at all.

I think the happy nature of the post-SKB destruction is justifiable in terms of movie sensibilities, but I did a super quick mockup of removing the fighters’ celebratory shots, shortening the following shot so the music matches up. You can still hear some of the vocals; this was just a quick mock up to get the idea across, and it will be easy to polish later:
https://vimeo.com/171864218