In my experience it's a lot like the real-life application of Communism; success or failure is dependent on the people originally in power being willing to give up a lot of that power to the people.

Agile shops that still have C-level execs shoehorning shit in at the last moment still have a lot fo the problems they did under any other methodology/philosophy. A lot of places here in the US will be on this CONSTANT cyclical hunt for some sort of "silver bullet" that will allow them to make what 90% of methodologies would label "bad calls" but still get all the benefits that require those bad calls not be made.

TL;DR: Agile-but is a lot more common than Agile.