Apparently, you need to start back at Cerberus HQ in order to get all of the new scenes. I didn't start from back there, so I don't know what any of them are.
Here's what happened in my ending (Two things: Mixed Paragon/Renegade, 100% All Assets, Liara LI, Destroy Ending.
Secondly, apparently at some point during the London mission before Harbinger comes in and shits all over your escapade to the Conduit thing, your squadmates get trapped and wounded under a vehicle, and Shepard calls the Normandy to pick them up. It sounds like an okay way of handling it, but I didn't actually see it. So I don't know):
From where Shepard gets up to where the Illusive Man dies is largely unmodified. There are one or two new things that have been changed: Hackett now says that someone made it to the Citadel. I can't remember if this part was in the original ending, but Shepard is now thrown out of the receiver node thing and gets tossed about a bit.
When you get to the Catalyst, though, this is where you really start seeing some changes. It makes its initial speech about how its solution won't work, etc. But now, you can ask it about itself, the Reapers, and the Crucible. Shepard doesn't blithely accept what it says and pick from three different color explosions this time, no sir.
What I find interesting is that, in my conversation at least, there's a lot more tension between the Catalyst and Shepard (I picked all Renegade responses). It seems resentful that organics have made its solution no longer viable, and it appears that it highly underestimated organics, and isn't happy about it. Shepard is far less tolerant of its explanations, reasons, and justifications as well. I personally found it to be a nice touch. The conversation seems less like somber, quiet acceptance between the two, and more like two people who hate each other being forced to work together.
That's a bland way of putting it, I know.
It's been noted that you can in fact get an 'Everyone fucking dies' ending. Either always pick Renegade responses, or shoot the Catalyst once you have to pick between Control, Synthesis, or Destroy.
If you pick Renegade responses, Shepard rejects the choices and says that organics will pave a future for themselves without the Reapers or the Catalyst. The Catalyst says, "So be it" in a voice that's frighteningly like Harbinger's, and you see two Reapers blow up two ships. The camera zooms out slowly, showing Shepard standing between the paths that lead to each of the normal endings, and the screen fades to black. It cuts to an Earth-like planet with a beacon, and underground there's Liara's hologram speaking.
The Stargazer scene now has a female talking instead of a man, and it's heavily implied that with the information that was left behind, the new civilization managed to defeat the Reapers.
Other than that, it's mostly the same as the original Stargazer scene.
If you shoot the Catalyst, the same things happen, but Shepard doesn't get a chance to speak.
Now, on to what everyone really wants to hear about: the modified original three endings. You're only getting Destroy from me, unfortunately. That's all I did.
The scene of Shepard shooting the power conduit is mostly the same, except that a memory of EDI flashes up, implying that Shepard knows that EDI will die because of what she's doing.
Everything is the same up to the Crucible being ready to fire, at which point Hackett says for the fleet to retreat from the Crucible. There's a brief scene of Joker frantically going through his holograms, presumably trying to get to Shepard, before Garrus places a hand on his shoulder and tells him that it can't be helped, basically. Joker concedes, saddened, and he heads the same direction as the fleet.
The Crucible fires, and we see the CGI scene of the Reapers falling on Earth. There's a brief scene added in which a soldier is trying to help another soldier along, and he's frantically shooting Husks, trying to keep them away. Just as the Husks are about to overtake them, the energy washes over the Husks and obliterates them. There's absolutely nothing left of them.
I have to say, it was at this point when I start to feel like the ending was recovering a little. It felt a little like I had picked 'Destroy', not 'Reapers trip and fall'.
We then get the scene of the energy beam shooting into the Sol Relay. This scene is also largely unchanged, but instead of the Relay blowing up, the middle part simply begins to break.
Then there's the scene of the beam chaining everywhere, which is completely unchanged. However, there are new scenes added. We see the Reapers falling on Illium and Tuchanka, the former having a brief scene in which the Asari soldiers hug and hold each other in realization of their victory, and the latter simply having the Krogan have a triumphant grin on their face.
We get the same scene of the Normandy falling, except EDI is completely absent, instead Liara in my case coming out first, then Javik.
The screen fades again, and Hackett begins to speak. He makes a large speech about the future of the galaxy, and what it took to accomplish such a victory. We see pictures of what happened to non-crew characters after the war (ex: We see Zaeed relaxing in retirement, Jacob making a speech to people, Kasumi going through an electronic handheld device), and small scenes of what happened to each of the races (the Krogan rebirth, the rebuilding of the Quarian civilization, etc.) Hackett somberly says that the victory of course did not come without losses, and we see shots of Thane, Legion, Mordin, and a helmet that either represents Shepard or the many soldiers who lost their lives. Hackett begins to talk about rebuilding and peace, and we see the broken mass relays, and the broken Citadel, the latter having another scene showing it restored to its full glory. We also get several scenes devoted to showing wartorn and destroyed places restored in the aftermath of the war with the Reapers.
Finally, we see the Normandy launch off the planet, having recovered from the crash landing, and we get a memorial scene, first showing the tombstone, slowly having the camera zoom out. If you look to the left and right bits, you can see the names of some of your fallen comrades that died within Mass Effect 3. In the middle, there's a large name plate saying 'David Anderson.'
We see a shot of all your crewmates (minus EDI) having their heads down, mourning their fallen comrades. In the middle is Liara, holding something in her hands. She walks over to the tombstone, but she hesitates from putting the thing onto the tombstone. It's of course a name plate, with the words 'Commander Shepard' embossed on it. She touches it tenderly, saddened. Her arms begin to make a move to place it on the tombstone, but she draws back, looks at it again, then looks up, smiling, implying that she believes that Shepard is still alive.
There are a couple of other signs that also point to Shepard surviving, such as some things that Hackett says throughout the speech.
(I'm a bit tired, unfortunately, so I can't remember things quite well. I think there was a scene that happened after the scene with Liara, but before this, but not sure)
And finally, the screen goes to black, but comes back in onto the scene everyone knows all too well-Shepard's breath scene. It's exactly as it was, completely unchanged. Then it cuts to black, and the credits come up.
After the credits, there's the unmodified Stargazer scene, then a redone final message from the Mass Effect team. It gives a brief recount of their feelings and experiences throughout the entirety of the trilogy, then signs off.
All in all, I have to say...I...like the Extended Cut. Sort of. It's still by no means perfect, but it's miles better than it was. There's some closure involved, I got to see what happened to some of the races, I saw the aftermath of my final decision and the future of the galaxy. There's better clarity, pretty much better everything.
There are some lingering threads, of course. There are still some holes that need patched, like how exactly Anderson got up to the Citadel with you, and the whole gun thing with the Illusive Man.
It's sort of but not really explained how Shepard could have survived the Citadel. The Citadel doesn't explode this time, it just gets damaged like the Mass Relays. In fact, one of the scenes shows the city parts of the Citadel, grey and darkened from the battle. So Shepard could still be in there and alive.
There were some things that weren't resolved, like what happened to the Rachni, and we don't get a reunion scene with Shepard and the love interest, but I didn't really need that.
Like I said, it's by no means perfect, but I can take it, appreciate it, and like it a bit.
I put it this way: the original ending made you feel like you had climbed a long, staircase, building up to the final victorious moment in which you reached the last step, and it turned out the last step wasn't there.
This time, the last step is there, it's just made out of granite and isn't as well shaped as the forged from diamond, straight 90 degree cuts that made up all the other stairs. But, the last step is there, and I appreciate and like that it is.
