I have proved that the free CyberBoard /Play by email system can work well in designing a game. My final playtesting was done in two ways. 1. The designer playing the prototype with the playtesters and 2. The playtesters playing independantly and the designer monitoring remotely through a spectator file. It answered questions instantly and allowed unmolested play to proceed. A great tool.
I have a new project and am using this system much earlier than the previous design. Links: http://cyberboard.brainiac.com/index.html
No, not the programmer. I just used it for what it does best: make your favorite board games come to life on the computer. It has a map making and playing piece design program built in. We played it by email and used a moderator to allow 7 others to play a very large game.
Instead of a bulky paper prototype, you can design in CB and send it to players for blind-testing.... the true test of a good game.