We started by hacking up the 2d platform sample game project that Unity bundles. Getting started was a bit rough, and the results from the first weekend were pretty buggy. Once we got to know Unity we were pretty happy with the decision though.

I'm sure that there are good resources for getting up to speed quickly, but unfortunately I don't have any recommendations for how to do it.

One suggestion that I can make is to stick to C#. Unity offers "Javascript", but Unityscript isn't really Javascript, and is more headaches than it is worth in my experience.