What I've noticed is that when the main product is software you show and tell everyone how it works. I did that with GN to my own list. I actually walked through how I set up my own page, how I chose the products and all that... then showed them how it made money and gave alternatives to Adwords.

The Good Dr. X already showed the guts of this site in the prelaunch video, but as most folks these days are a bit skeptical I figured a bit of my own personal take would go a long way.

However, as Mr. Freville pointed out it can be taken a bit too far with a simple info product.

Be smart about it, and if you're really good you can show your results after having used it. (hint, hint)

Another thing I've done which seems to work very, very well is to review and then hit them with the fun bonus I figured out while using the product personally.

Like during the review you find 1 or 2 things which seem a bit "off" and you can just make a fast bonus or patch to help people blast through.