The results have been mixed. It does produce good simple components using the system. There is a handy sandbox for testing and it's easy to download a completed component for more detailed work.
In general it's a good product. It allows you to do most of the hard work of building a component in the MVC structure. However there are limitations. Perhaps the biggest I found was the inability to achieve all but the simplest of table relationships. It does 1:m but not n:m. In practical terms that means that if you had a post and you wanted to attached a series of tags to it that would be okay. But if you wanted to attach tags to multiple posts (a many to many relationship) then you can't do it.
This lack of many to many is a bit of a problem since any substantial component will need to use this at some point.
There are other limitations too, for example I couldn't see how to use a multiple key to create a join between tables - needed to use the existing user management system within Joomla.
Alll of that said if you're looking for something to cut out some of the work of building a component and you can live with the structure then it's worth a shot.