I presume you're referring to the design of the model itself in the studio, rather than the application in the browser.
The main strength of Tersus is the management of the flow of complex business logic and the unification of server side and client side development across multiple platforms. The current design seems to fit pretty well with the flow paradigm, but of-course we're always glad to hear suggestions for improvements. And remember that since this is open source, it is possible, though technically challenging, for you to implement a completely different design.
I haven't played with App Inventor, but from what I've read it looks like its "visual language" is basically a visualization of the hierarchical structure of a conventional programming language. I can't say how valuable such a visualization is (tools like Eclipse already give a decent view of codebase hierarchy). I'd guess that Google has done a decent job in making the simplest things easy. It will be interesting to see if it scales to real life enterprise application.
For best results, use the Firefox browser..