Finally finished the War in Heaven part. First time I tried to do a BP playthrough on hard, and boy were some of the missions tough. But anyways!
I'll start with the voice-acting:
Thoroughly enjoyed it. Yeah, there were some voices I enjoyed more than others, but nothing that would have tilted my enjoyment in any way. In fact, some of the voice acting was outstanding. Several of them were already named on previous pages, and I can only agree. However, I would like to make one special mention, and that is Simms voice acting in Sunglare. That was first-class.
The music changes, although some were quite subtle, were, for the most part, very good. For instance, I loved the different ending in the Delenda Est briefing music (I didn't think that mission could get any better btw, but somehow it did. More on that later). Other changes I liked were the main menu, the amb music that plays during For The Wrong Reasons, the combat music that plays when you get ambushed during The Intervention, and finally, when you smack the Carthage with the Toutatis' air wing in Her Finest Hour.
Speaking of Her Finest Hour, there's also a change I didn't like. I rather liked the music that played in the opening stages of the mission. It gave the whole battle a kinda-badass feel to it.
Onto gameplay changes! Post Meridian was a brick wall for me. Not that I failed so often because I got obliterated by the cruisers (and oh boy, I did this time around), but because every time I lost a single gunship, the Meridian kinda butchered one of the frigates. The other thing that happened the first three times or so, was that I got tagged. That was fun for the few seconds it lasted. Don't get me wrong though. Yeah, the mission is a ***** to beat on hard, but I had an absolute blast.
The other mission I had terrible difficulty with was The Plunder. And I'm afraid that was one that wasn't very fun. Maybe I just totally forgot how to do the mission, or maybe it was that I was playing on hard instead of medium, or maybe it was the new Hyperion model, but the first two or three minutes basically consisted of me firing my paveways and then just staying completely out of the battle until the cruisers were engaged with the frigates. Because the second I was anywhere close to 1.5k km, I got splashed by a variety of beams.
Finally, there's Delenda Est. As mentioned above, the ending of the briefing music is somewhat foreshadowing if you know what will happen next.

Having to destroy the entire air wing before the Katana and Altan Orde arrive makes it just that more climactic before... y'know.
The new models I all like. The Erebus, Titan, Hyperion, Kumari etc. all look good, but the Titan, in my opinion, is the absolute best one. Sooo gorgeous now.
As for the Act 3 changes:
The dialogue changes are very good. As someone who hadn't read all the threads in this forum before my first playthrough I was somewhat overwhelmed by all the information in Act 3. Obviously I knew more this time around, but I still feel the rewritten dialogue helped a great deal. But more than that, the changes helped me to connect with my wingmen, which wasn't really there the first time. I mean, it's not like they were bad or anything, it's just that they didn't have the same feel Brie, Kassim or the Wargods had. I'm happy to say it was different this time around. It wasn't just them talking to each other (which was a really neat feature though), but the way they interacted during the training missions. The Custos training thoroughly made them click for me. That said, would it be possible to move the Vasudan Knossos a bit closer? The guy was interesting, but it was a bit annoying to fly 40k km every time.
The training helped me to finally figure out how to hack one of the Mjolnir guns in Everything is permitted. Was glorious to see Henriksson get smoked by one of those cannons. However, I did encounter a minor bug here, but more on that later.
One Future was a bit like Post Meridian for me. Tough as nails, but very enjoyable. It didn't help that this time I showed mercy to the Gefs in Nothing is True, which resulted in me having to combat two more Gef cruisers. The perks of being a good guy.

For Her Finest Hour, the training helped for sure. Managed to get 'Excellent' on the first try, largely because the training prepared me this time

. As mentioned before though, I preferred the old music for the first part of the mission.
How beautiful is that new interface in Eye of the Storm? Also, was that the famous SOC Skin for the Nyx's I saw in this mission?

And that, unfortunately, already brings me to Universal Truth. Still ultra creepy of course, but I enjoyed the changes. However, the tunnel (?) I was flying through was a bit confusing at first, as I seem to remember flying through a nebula the last time. On a more humorous note, when I got back into the dreamscape at the end of the mission, my wingmates seemed so happy to see me that they kept trying to hug (Read: ram) me.
As for the final cutscene: That was a horrible thing to do. The cutscene was so good, so teasing that it'll make the wait for Act 4 unbearable.

Now, I did encounter some minor bugs. I never saw my full loading bar, only the very end of it, which isn't a big deal. Also, during Everything is Permitted, the Argus complained about strange activities at the Mjolnir twice. Once when I hacked it, then again when the Elder's transport got blown to bits. The final issue I had, was that the dialogue in Universal Truth was very quick, much quicker than usual. I'm usually a very fast reader, but had trouble keeping up with some parts, in particular the dialogue with Ken near the Capella star.
But overall, a spectacular release. Can't praise it enough, just incredible work.