How done it looks implies how done it is

Kathy Sierra and Dan Russell have an excellent article on prototyping and how the prototype influences the audience
http://headrush.typepad.com/creating_passionate_users/2006/12/dont_make_the_d.html

Makes very interesting reading. Have to admit I have fallen into this trap before and spent some time persuading people that the application is not as advanced as the prototype could make them believe. Matching the maturity of the prototype to the maturity of the application makes a lot of sense.