I might as well write about this while it's still fresh. Oh, and there's going to be epic Mass Effect 3 ending spoilers. You've been warned.
Within the past 28 hours I have replayed the end of Mass Effect 3 with the Extended Cut DLC. I had two characters, one was mostly paragon with high galactic readiness (Obamashep), and the other was the devil who made all the
bad renegade choices (generally killed everyone) with weak galactic readiness.
As noted previously, I mostly liked Mass Effect 3 apart from the last 10 minutes or so. So lets see if I can take it from the top (from memory!).
I don't think anything really changed (aside from cinematics maybe) until you get to the forward operations base in London. Garrus might have had something extra to say, and Liara gave you some farewell memory (don't quite know what that was). Nothing else of note happens until you make the run for the light.
I previously noted how the crew members that you had chosen for the mission were nowhere to be found after you blacked out. Now the Normandy swoops down from space to pick up your bloody comrades under highly questionable reasoning (had to fly close to a big Reaper). You are given no support, supplies, or backup. Then I blacked out running for the light, and Shields' head popped open like a ripe melon as usual.
The godchild is still there, with his old logic. Goes something like: "Yo dawg, we heard you didn't like being killed by machines, so we're sending a bunch of machines to kill you, so you won't be killed by machines!"
I think you can prod the godchild a bit more on the options, but this time, you can tell him to shove the options where the Sun can't shine. Then he says "Fine!" in some deep, ominous voice and you are left there. Everyone dies, and there's a cinematic that shows Liara's hologram box playing at a archeological dig site, presumably many thousands of years later. A harrowing end.
The other options are rainbows and unicorns compared to what they were before. It seems that the relays were not destroyed, they are just majorly damaged.
After Shepard controls the Reapers, there's this deep voice narrating about Shepard, in a way that makes you think it's him speaking, but then there's this whole third-slash-first person dichotomy about it that makes me totally uneasy. That's aside from the fact that the Reapers are rebuilding everything and protecting everyone.
When you choose destruction, it depends on some factor between my characters whether or not a lot of people die. For Obamashep, most everyone survived, but for the devil, I saw pretty much everyone be vaporized by the blast. Admiral Hackett narrates. You see the Citadel in Earth orbit, heavily damaged. He speaks optimistically about what we can do together now the Reapers are gone.
Synthesis results in a pure rosy utopia. EDI narrates. Reapers help rebuild, with the knowledge of past species for everyone else to learn from.
If your readiness is high enough, the Normandy (after crashing on that jungle world) takes off. But before doing, a teary-eyed crew member (romance interest, possibly?) places Shepard's placard on the Normandy's memorial. Very nice touch in my opinion. London is rebuilt, but I'd think that with 90+% of everyone dead (inferred, citation needed), it would take decades of work to rebuild the place. The existing characters shown have clearly not aged at all. Cities would be smaller, fewer, and further between. The relays are shown being repaired.
Several scenes dealing with what you did to the Krogan are shown. Whether it's desolation and extinction or hope for a bright tomorrow. There's only one for the Quarians and Geth, though.
The original ending was a turd, plain and simple. The Extended Cut DLC is a polished turd; it looks weird, and you might even show it to your friends, but it still smells funny. For many, this comes too little too late. At least someone's enjoying it.