In general it abstracts away the specific UI used to present a tool and I'd say that was generally useful. Anyone wanting to experiment with a novel UI could benefit from ToolBuilder. In Squeak trunk there's even the ability to test it against Morphic and MVC. MVC is still useful for those trying to build minimal images.
MVC was removed in Pharo in 1.1... Why not make Morphic compact instead of keeping MVC? There is quite a lot of code everywhere in Squeak dealing with MVC compatibility.. very hard to clean up anything. E.g we removed Paragraph... and merged all multiple Paragraph classes of Morphic into one (called, ahh... Paragraph). E.g. getting a new Canvas would for shure be much harder if we would have kept MVC.
I've found ToolBuilder useful for constructing new UIs, editing existing ones and being able to follow actions without needing to know much about about Morphic.
Why not make Morphic easy to use instead? Wasn't it supposed to be easy? Marcus -- Marcus Denker -- http://marcusdenker.de