One of the big-brains on the ASP.NET team is blogging about developer personas and how they apply to the real world work he is doing on V2.0 of ASP.NET.  Comments on his blog are also very interesting.  Steven Clarke has been blogging about similar topics in the past... Check him out as well.

I certainly find it the model valuable to help put some order around our thinking about features, but it should never become a hard and fast rule.