I'll just say that I didn't hate the original ending, but I totally understood the backlash that resulted from it. My only problem with the ending was that it was too open-ended... Was it the end of the universe? Was your crew permanently stranded on that planet? Were the millions of Citadel residents suddenly killed when it exploded? I just found it didn't have enough closure, especially for the finale in a trilogy. Fortunately, the extended cut DLC answered a lot of the questions I have, and now I have a better idea of where BioWare might take the universe for its next entry, which is really all I ever wanted.
My other only complaint with the game was the whole Return to Earth chapter, right before the finale. After spending the last 30 hours accumulating war assets and going off the beaten path to gather as many people as I could, I was really hoping my efforts would have paid off in some tangible form, rather than just be represented by a number and green meter on a computer screen. As a result of my choices, I would've liked to have seen geth fighting alongside the quarians, or turian ships performing airstrikes, or team up with a group of elcor in an assault. Anything that would've said, "here, this is your bonus for going on that side quest and getting those extra war assets."
Other than that, it was a fantastic experience, and is still probably the best game I've played all year.