Definitely. At the end of the day, the best way to get any kind of funding is to make people worry that they're missing the boat heading towards a ton of money. Demonstrating real customers, and everything else that falls under 'traction' and 'momentum' is the way to achieve that.

If I had to do it again, I'd completely forget about the money-raising and spend the three months focused on the product, and worry about everything else much later. That's not a great fit for the Techstars program, though some of the most interesting companies to come out of it have ended up boot-strapping, eg Occipital/Red Laser.