I just found this useful blog entry, even though it is a few months old. It is from The Demo Coach Playbook.
Basically, it says:
- It's a good thing to answer a question with "I don't know" so you can have something to follow up with after your demo. Also shows that you are human and not a know-it-all.
- Don't have your demo come off too smooth or slick, or it might not seem real.
Nice things to keep in mind when so many of us Microsoftees present demos.