When I've asked vendors if they leverage Agile practices, I've discovered many shades of gray. I'm sorry to say, I've seen people pervert the original 12 principles of the Agile Manifesto to the point the mere mention becomes the punchline of jokes. It's easy for me to become incited, when Agile becomes the scapegoat for poor leadership or process. I still believe the 12 principles are the framework in which we decide if Agile is still agile. If the Manifesto is no longer the Agile bellwether, perhaps it should be refined?
Agile will stop being agile when we start to detail all possible inputs and outputs and actually believe we can predict or plan our way out of every situation. I think it will also stop, if the Agile community as a whole, disagrees with the Manifesto. All laws can come before the U.S. Supreme Court and be argued as to their constitutionality. Sometimes I wish projects or activities within Agile projects had a measurement of their agility and then blessed by a governing body. Granted, the Agile Manifesto is not the U.S. Constitution and the Agile community does not need a Supreme Court.
The best measuring device I can rely is my own limbic system; My gut feeling. I'm sure you know what I'm talking about. It is not as easy to say something feels Agile as it is to say it does not feel Agile. When did this all become so overly complicated?