The ending of ME3 seriously taints the entire series for me. It's that awful. I wasn't expecting something amazingly heroic, but I also wasn't expecting them to finish it off with some stupid Soprano's style ending that makes no sense and doesn't change no matter what choices you made.
I'm probably never going to buy another Bioware game again until it's been thoroughly vetted by the court of public opinion first. I thought that DA2 was an anomaly and figured they couldn't screw up Mass Effect, but I was wrong.
There's a video online showing someone editing a couple flags in one of the game's data files to enable the Prothean character in a regular version of the game, so the DLC thing was just a pure cash grab.
EDIT: Several major retailers are apparently dropping the price of the game already.
Bioware also has a post on their ME3 forums basically stating "we know you think the end of the game is bad, but please stop spamming our social media sites with complaints because it's... uh... ruining the end for other people."