By itself I think it will be fairly useful, but it really shines when you combine it with their Hollywood Camera Work DVD course, which is brilliant. I firmly believe that every person here should save up the $300 and buy this course because it teaches you how to shoot fantastic-looking easy-to-edit sequences using a minimum of cameras. I've watched the first two DVDs (static cameras) three times through, and the next two (moving cameras) twice.
I will continue to watch repeated viewings to absorb the ridiculous amount of information they provide. It's basically a 4-year camera course crammed into six DVDs and is worth every penny.
The moving-camera DVDs convinced me that I absolutely need a dolly for my feature -- it's not just for moving-camera shots, but shows how to block out a scene where the tracking cameras also double for fixed cameras, drastically cutting down on the number of setups you have to do, while also giving you a lot of moving camera shots that naturally fit into the flow of the scene.
Armed with this information, the Shot Designer app goes from being a nifty little utility to being absolutely crucial in shooting efficiently and preventing you from wading into an editing nightmare later.