How to position a new release?

Does a new release make it harder to position your value?
Are you stuck thinking about the new shiny features and talking less about the overall value?

Has the overall value proposition changed? 
If you are offering the same benefit areas as before, then the headline value isn't radically different from before.  Getting straight in to demo the new features isn't going to sell the product better.  There might be some corner cases of individuals who understand your product and market so well, that they just need to see those things.  Your average buyer will need to understand the value proposition as before.

What do you need to change in your demo?
You need to think again about what are the best capabilities to show for each customer which back up the overall value proposition.  Don't just extend the typical harbor tour demo to include the new things.  Look for better ways to back up the value and show these.

When should I change it all completely?
Sometimes your product update will introduce new areas of value to new customers. Sometimes the marketing changes to have customers come to you in a new way. Your product may change visually so that your old demo no longer works, or you need new data or stories to show.  In these cases you should reconsider the value proposition, and then think about a demo script which addresses the value and shows the relevant capabilities.

The best demos will showcase the value of your solution to the customer, and cut the time that it takes them to understand how it will work for them.  Don't waste your time and risk losing the customer's attention by showing a chronological history of your product and problem area.