A member of a team I'm coaching told us she spoke with an old friend who asked how things were going. She mentioned the team started to adopt agile development practices several weeks ago. Her friend was appalled. "That's terrible!" she exclaimed. (The quoted passages are paraphrased, of course.) "You'd better start looking for a new job right away! We tried agile, and it was a disaster. Everyone hated it. Thank God we've stopped doing it!"
Our team mate said she laughed out loud and tried unsuccessfully to interrupt her friend's rant. "I don't know what happened at your company," she said (when she could), "but that's not how it is here. It's been really good for us. We've established good velocity, we've been cleaning up the code base, our customers are happy, and there's a lot less stress than there used to be. I don't know what went wrong at your company and I'm sorry it didn't work for you, but we're doing fine."
I don't know what happened at the other company. All I can say is that this team understands agile values and principles properly, and is fully empowered to self-manage within well-defined boundaries. I think those two points are critical success factors for getting good value from agile methods.