The "webui" system from Cinemon makes it really easy to model a system of objects rapidly, automatically generating a functional interface for manipulating those objects. However, unless you are intimately familiar with the model, it's rather difficult to work with the resulting system. Most of the redesign (beyond simply making the project look better) is going through and hard-coding various views into coherent overviews of multiple objects rather than browsing individual objects or collections.
A.B. Strakt's content management system seems to suffer from this problem as well; to understand any application built with their framework, you must understand the entire application. According to Jacob, they don't have a mechanism available to override the user interface... which makes it very problematic to actually use the system for anything beyond prototyping. The problem is that to provide this kind of customization is almost always going to be rather kludgy compared to the base framework... life is often messier than computer science.