So... wow. First, the actual new ending feels like such a "screw you" to the people who hated the endings in the first place. It's almost funny.
You want to refuse the star child? Well, there you go!
The actual "canon" endings though are... I don't know. Probably the biggest thing is that they completely retconned the destruction of the Relays in all the endings, so no more stranded fleets all across the universe. But otherwise, the endings are still basically the same with a different ending narration flavour text/voice over tacked on. Synthesis still doesn't make sense to me as an idea because of what it represents - forcing everyone to become a synthetic whether they want to or not.
They also don't explain how Shepard survives the Destroy ending at all... the "breath" is still the last thing you see before the credits if you pick that ending.
And funny enough, they fixed that idiotic Joker thing where he looks behind his shoulder as the Normandy is about to get caught up in the Citadel blast shockwave thing.
I don't want to say that it in any way fixes the ending and if anything, I feel it shows that they didn't know what they were going for in the original ending in the first place, but I have to imagine that at least a lot of the complaints have been addressed.
Once and for all, I'm glad to wash my hands of this franchise and to move on to better things.