[Please forgive me for posting this response on my own blog, but the editing tools are better here than your comments form, and I get to keep a copy of my thoughts!! ]
In response to your article "Activity-centered Design" published at http://bokardo.com/archives/activity-centered-design/ I would like to offer the following...
I agree wholeheartedly that ACD is a valuable, well-directed, and successful (ie proven) approach to the design of digital (and physical) products and services. However, I disagree that it is superior per se, and I'll expound on that thesis during the rest of this response.
Firstly, to my mind (and in my experience) the key factor determining the success of a methodology is the skill with which that method is applied. The second key factor is in the suitability of the methodology to the project.
Your (team's) ability to successfully apply an ACD methdology relies on a combination of capabilities, people, experience, and tools. Once you've decided to focus your attention on the application of ACD to your projects, you need to cultivate your ability in those capabilities that are most critical to the ACD methodology. You need to hire staff with the right mix of skills, who have the attitudes necessary, and who are skilled at working together in appropriate ways to make that happen efficiently and effectively.
Now, let's say I decide to follow a User-centred design or goal-directed design approach. What I will be doing is hiring staff with a necessarily different mix of skills and expertise; deep capability in other aspects of UX architecture and design; able to work together in a different configuration and on different tasks than those your ACD teams is doing.
Finally, when each team - ACD, UCD or GDD - is approached to undertake a specific project we will put together a plan of action that plays to the strengths we've developed within the broad context of our chosen methodology. The ACD team might modify their approach to bring it closer into line with a traditional UCD approach; the UCD team might modify their's to bring it closer into line with a traditional ACD approach - by emphasising certain tasks over others.
In my own experience, ACD is best applied to projects wherein the needs of users have little or no impact on the collection of tasks that are required to satisfy the activity being undertaken. I have in mind sites like harvestapp.com, rememberthemilk.com or flickr. Where the user audience is not homogeneous with respect to the core purpose of the site/application, then I (personally) find ACD to be less suitable, and an alternative approach needed.
However, this belief is based on my own capabilities, knowledge and experience. I necessarily tend towards the methodology (as a collection of tasks in a particular order) that plays to my strengths and allows me to best apply those strengths to the problem at hand.
All I can suggest is that you - and your team - do the same.