Criteria for a Scrum Tool - or any Agile tool, that is

In one of the many mailing list threads on tools for Scrum teams, I posted a list of evaluation criteria that I'm quite happy with. So I decided that it might be worth a blog entry. Anyway, here they are:
In my view, there is one universal evaluation criterion for any Agile tool:

• does it provide what the team needs, in the simplest possible way?

To support self-organization, I'd probably add:

• did the team itself choose the tool?

From personal experience in small, colocated teams, I'd add a whole number of additional criteria for that context (in no particular order):

• is it highly flexible? Can it easily be adjusted as the needs of the team change over the course of a project?
• is it intuitive to use? Can I use it without having to think about it? Does it feel natural?
• is it highly visible? Can I see the current data without any effort, at a glance? Even by just passing by, or by looking up from my screen for a moment?
• is it highly collaborative? Can several people stand together and discuss with each other, with everyone having the same chance to work on the tool, and see and influence what everyone else is doing; concurrently on arbitrary different parts of the data? Do people notice when I look at it? Does the tool help start necessary conversations?
• does it provide easy navigation between high level and detail views? Is it possible to get a feel for the state of the Sprint at a glance? Is it easy to spot anomalities, and to dive into details?

The most appropriate tools I know for those requirements (again, remember that this is for a small, colocated team) still are cards on a wall and manually updated graphs on flip chart paper.