Eric Lippert has a great post about ZBB.  This is probably the second or third really good post from a Microsoft person about this topic (if I can dig up the other posts, I'll link to them).

I love the concept, because many projects I've worked on (mostly when I worked for a “consulting firm”) have been in the “let things get worse and worse, assuming that you'll have time to fix all the bugs just before release“ category. 

I also liked his take on working in an “open” environment; “It was definitely a good thing to try, but I think it works best as an emergency measure rather than as a day-to-day practice.“  I agree.  I've worked in a bullpen-type office and all I can say is that it sucks for anything other than short-term sprints. 

I'd sure like to see what Microsoft uses for their internal bug/task/feature list database.  One of my back-burner projects is a project management tool that incorporates issue tracking, tasks, project artifacts and overall project status reporting.  Maybe I'll resurrect it when my current project slows down.