I would agree with most of the comments made above, adding the following:
1. Remember that the bluetooth will not let you dial whilst moving, or even select an entry from the phone book! That is of course Nannying gone mad, but it is a major inconvenience.
2. The DVD will not play images whilst moving, so has very limited functionality.
3. You cannot add speed camera POIs to the Sat Nav, again a major inconvenience.
4. There is no 7-digit postcode search in my 2007 model, I believe it is still the case with the 2008 models.
5. Most annoying of all you cannot enter destinations whilst moving, a safety feature which will ensure that if I ever buy another Lexus I will never specify a built-in Sat Nav system again.
Of course you can over-ride nos. 1,2 and 5 with major hardware surgery, but it's a hassle.
Good luck!