There's this new development that I have found myself driving around in this week and my nav doesn't know it exists. Anyone update their navi recently? How much does this cost and is it something I have to see a dealer about?

 

Most all the information you may need can be found here:

http://www.lexusnavigation.com/

You can see how to find what version of the maps you have, the latest version information, etc. Your update is provided by the dealer via USB and cannot be performed by the customer.

As the development is new it may not even appear on the latest map.