Well, I've at long last completed the Mass Effect trilogy and experienced for myself the oft-criticized ending. Here are my thoughts:
From the time you put boots on the ground in London, the game is incredibly buggy. At one point, I needed to survive a protracted battle until my team could be evacuated, but the shuttle never came, I killed all the bad guys, the battle music kept playing and game-play was essentially stuck. So I had to go back to my last save and fight the whole battle again, at which point the shuttle did show up when it was supposed to.
Shortly thereafter, one of my team members was killed in battle (I found her body), but I was unable to resurrect her. However, she was listed as living, I continued to talk to her as though she were alive and at one point her disembodied voice began to answer me. This went on for nearly half an hour of game-play mostly comprised of battle until she magically returned after a cut-scene.
At that point, I switched from the 'Normal' play setting to the 'Narrative' play setting because I was close to the end anyway, didn't want to have to play though any more major bugs (Seriously Bioware, you couldn't QA the game a little longer?) and wanted to see how the story itself played out.
I was a FemShep Paragon character who had a readiness rating of over 3700 going into the final battle, so all possible endings were available to me. I played through the two that interested me and one more that I rather stumbled upon by accident (the 'I refuse to make a choice' option). Honestly, I liked the lack of a final boss fight and the philosophical nature of the climax, which suited the end of this long and complex story quite well. However, the fundamental conceit of the entire trilogy - that the catalyst AI was creating synthetic life to destroy organic life so that other synthetic life forms would never evolve enough to kill the organics who created them - was an object lesson in amateurish writing that should have been spotted and resolved before the first pixel was coded. Yikes. Nose-bleed stupid, that.
Which brings me to another failure in storytelling, one that Bioware has suffered from before; difficulty writing a denouement. Neverwinter Nights: Hordes of the Underdark did make a respectable effort to honor the emotional investment players had made in the tale with a 'how the world has changed because of your character' epilogue, and Dragon Age: Origins was downright bookish (Thank you, Brent). But KotOR slid from the boss fight to the credits with a brief stop along the way for a cheering crowd, and Mass Effect III forgot it was a story until the fans demanded to know how Shephard had changed the world and the characters they cared about. And the denouement Bioware offered? It was a shoddy afterthought to nearly a hundred hours of game-play that deserved a better, more emotionally satisfying conclusion.
In all, the Mass Effect trilogy was an ambitious and mostly-successful fusion of game and story I'm glad I invested the time and money to play. But while Bioware writers are fond of boasting that writing for games is different from writing for publication, never is that more apparent than when a role-playing game falls flat on its ass for lack of a basic storytelling skill that would prevent a professional writer from being published until it was learned.