We need to step back here and ask if, just maybe, everyone involved in this debate is saying roughtly the same thing. Rob Bowley's view is, basically, that Kanban is overhyped. Yes, it's useful, but not that useful. David J. Anderson explains his understanding, that Kanban disperses information and decision-making power throughout an organization, and thus keeps projects on track and gets attention to them before they go off the rails.
Here's what neither of them would disagree with: Kanban is part of a set of best practices, and it's especially good at getting people to focus on what resources or efforts are needed.
Kanban might be "just" a tool, but tools are hugely important. Learning is a process of picking up new tools, most of which you store in your head, some of which you keep on your hard drive. Learning to see things with a new perspective, to see the goal and not just the process, and to act as a leader when leadership is what's called for — that's what Kanban brings to everyone on a team, and that's why it's so powerful. The tools you use define how you think (whether they're the words you use to talk or the project management tools you use to lead your team).
In an early post, Rob Bowley nailed it (quoting from this discussion from The Toyota Way):
TPS experts get very impatient and even irritated when they hear people rave and focus on kanban as if it is the Toyota Production System. Kanban is a fascinating concept and it is fun to watch… When is the kanban triggered? How are the quantities calculated? What do you do if a kanban gets lost? But that is not the point… The challenge is to develop a learning organization that will find ways to reduce the number of and thereby reduce and finally eliminate the inventory buffer… So kanban is something you strive to get rid of, not to be proud of.
There it is. Like magic. Kanban is a tool for spotting problems. Not something you want to be part of your life forever. Once your team has established some serious Kanban momentum, you don't have to push the process so much. Instead, you can just watch the results.
Kanban is a great tool for bringing out the leaders in your organziation. It's not going to turn people into leaders, and it's not going to magically improve your productivity. It is one more tool you can get a lot out of. And that's something worthwhile.