the best part I thought, really, was Darth Vader showing up and tearing ass through everything, as we were always told was something he was good at. Until this movie, the only visuals we ever got of bad-ass Vader was of a petulant little bitch slicing up some weak children. The stupid joke aside, this was the best Vader yet, imo. But I also think they could have adjusted the timbre in the voice because JE Jones sounds way too old. It's weird that they didn't fiddle with the voice, considering the $$$$ spent on tapping our uncanny valley sensitivities with some creepy cartoon characters that totally did not work. (I was way too busy being creeped out by Tarkin's side-speaking and videogame zombie shuffle to pay attention to anything he was saying.)
TO address something earlier re: How can the rebel fleet hold off a couple of Star Destroyers and then get decimated as soon as a single Star Destroyer with Vader shows up? Well, that's because Vader and long-standing Star Wars mumbo jumbo that you (the audience) should be long-conditioned to accept by now. A Star Destroyer (or fleet, for that matter) commanded by an unnamed "chokable" Captain is nothing like a Star Destroyer commanded by a Sith Lord, or Jedi for that matter. Those dudes' powers stretch beyond the things immediately in their presence and they are able to turn the tide of battles simply through their machinations with the Force.
If Vader is the supreme badass he is supposed to be, then considering various other powers of other sith lords, Vader would have the power to crush any number of small fighters, and even life-support/fuel systems of large frigates or whatever, simply by willing it. To me, there is nothing odd about Vader's Star Destroyer showing up and single-handedly decimating a fleet. That's pretty much why the rebels are constantly in hiding at that point and very much unwilling to commit a large contingent to such a mission, much less their entire fleet. The chance that Vader would show up is just too high.