From my experience, it's more informative for customers to see a Flash presentation to understand software and similar types of "explainable" offerings.
This being said, if it's presented nicely, a TV-like advertising for things like travel might be appreciated by visitors. In all instances, make sure the video (or Flash presentation) is optional and cancellable at all times or else you'll frustrate a part of your audience wanting out, at some point.
If you ask me, it's TV that's trying desperatly to integrate the web more
