|Please don't change it. Just "new" it.|
But, honestly, there isn't any difference between a new product and a changed product. It's all in the packaging. Not the physical packaging, but the marketing.
The way a product is branded by marketing will inevitably create the consumer perception of the product's update. If marketing can create a "new" perception of the product, like the always brilliant product marketers at Apple did with the iPad 3, consumers will buy in. It's much more difficult to sell a product that's just "changed."
Just think about it. What are some other "new" products that were well-received by consumers, and some poorly-received product changes? Add them in the comments below or Tweet them at me @RyanPratt.