If you mean the product that's in the youTube vid below, I think it's a great idea for peeps who don't already have NAV. Looks like when you buy the kit, they include pre-wired harnesses based on your car and model so it's a fast, easy install and you don't need to make changes to the outside of your dash. I wouldn't replace my factory NAV with it, but I didn't hav NAV, this is what I would buy. I assume since it's Garmin, you can also get updated maps, etc for the system each year.
http://www.youtube.com/watch?v=LwjFdxZky4Y