The gist is this: run a single command yo web-data-connector, answer a few questions, and it scaffolds out the app. Run grunt, and you have a working copy running on a local server. As you save changes, it validates your syntax / style and recompiles your source code.
Easily test within the SDK simulator, or within Tableau itself. It also stubs out some automated tests (run them with npm test), and gives you a scaffold to do the Continuous Integration thing.
The hope is that it will take care of a huge amount of boilerplate code for you, give you a first-class development workflow, and let you crank out a large number of high quality connectors for all the data you need to connect to.