Traction is king.

Your goal is to communicate traction over a period of time. Check out Brendan Baker's quora answers:

* http://www.quora.com/Brendan-Baker/Posts/Startups-How-to-Communicate-Traction-to-Investors
* http://www.slideshare.net/brendanbaker/how-to-communicate-traction-to-investors-with-brendan-baker-and-hiten-shah

"Traction is your story of momentum, communicated through quantified evidence of market demand for your product" Brendan Baker & Hiten Shah.

At different stages of corporate development you can convey different levels of traction. Early, it is about vision and the ability to build a team and early product. But the story needs to evolve. If you are still talking about vision after 4 months, you should go back to the drawing board.