My understanding is that the NAV system has not changed at all, and the antenna is still not exposed.
The shark fin antenna is for the sat radio, as EVERYONE was complaining about the after-market antenna being installed with the sat option.
where is the nav antenna, anyway?
After my first question about the "shark-fin" antenna, I continued to look around. I did a search and found several hits that did say that the S-F antenna will be for XM satellite radio. On the Lexus site under Press releases, http://www.lexus.com/about/press_releases/index.html there is a note for the GS that indicates that the new S-F antenna was for satellite radio and it says that the IS will also get this antenna. I called Lexus and they confirmed that the S-F antenna on the IS is for satellite radio. There shouldn't be a need to add the crappy looking after-market antenna on the trunk. You may want to conatact your dealer and ask them about this. I bet the IS is now pre-wired for the antenna and it terminates close to where the XM box goes and just plugs in to the box. If you get any better answers, let us know.