I enjoyed the gameplay. But the plot was mediocre at best, and the endings made the game downright not worth buying.
I could understand their concept - it was a good one, but I get the impression EA put a lot of pressure on Bioware to leave it somewhat open-ended for them to roll in and make some crappy Online thing, as is the current craze.
Either or. I was disappointed with the endings and the plot leading up to them, as much as I appreciated the... idea behind it all. (Felt too Matrixy for me, I will admit, consider Shepard to be Neo, Reapers to be the Agents and the kid to be the Architect.)