Bottom line. They have you. The update is $300 period. I have the nav. and I personally chose not to update. I wish Lexus would just team up with Garmin, like they did with Bose. Leave the nav. to the pros. They should let you update on-line - what is this the 15th century?
I still mapquest things if I am in a rush (especially on business trips) just in case.
The best part for me is when I am at a late meeting at say 11 pm and I say home... and it takes me there

Wife just got Acura MDX, there is no lock-out while driving - which is a huge complaint on these boards (which BTW I am not sure is a great idea given what I have seen in action!), but interested to see how the system compares in terms of map and address accuracy.
Although... I love my IS - so forget the TL.
My IS rocks...