I work at Trello. We actually don't think of Trello as Kanban. Trello at its core is a collaborative list of lists. You can use Trello to implement a Kanban workflow but Trello is not an implementation of Kanban. A lot of people use Trello for things like to organizing their soccer teams where there isn't a hint of Kanban -- each list could be a game and people add themselves to indicate that they want to play.
I think the great thing about Trello is simplifying down to a pure visual metaphor.
Trello is about putting lists of cards on boards. That's it.
You can use it to do all kinds of things, but it's a medium rather than a framework. When I've tried other to-do list apps, or project management tools, etc. they all end up becoming too restrictive. They try to teach you to do the right thing in the right way, not realizing that it is different for different people.
Joel himself once talked about Excel, and how for most people, Excel isn't about spreadsheets, or formulas, or calculations - it's about laying things out in a grid. That's it. People just want to be able to write things in columns and rows, and colour them. And that simple behaviour is incredibly powerful.
> "Trello is about putting lists of cards on boards. That's it."
100% this, for me.
That's how I'm able to get people to use it. They ask a lot of questions about what means what and assume it's more complicated than it is. As soon as they realize that the top level metaphor is seriously just a board with cards, they're like "Oh! that's really cool. I can use this" and they're off.
I don't think that's what he/she meant, I don't even think the 'kanban' was about Trello. It's about taking something relatively simple, then honing it to perfection. That is how you make great stuff - not by building something huge that only works most of the time, and even then only satisfactory. Kanban is about small improvements every day, for many days, applying the power of compounded improvement so to say.