I just picked up my 07 IS 350 w/X Package and I am impressed. Car is very well optioned at a fractional price compared to my other car E55. Lots of power for such a small car, Navigation is superior over the Benz's one. A fun car to beat around on a daily basis. Highly recommend the X- Package for anyone who is looking into getting the IS 350.
Sport tuned suspension is a MUST, backup camera is cool, bluetooth is marginal but my favorite is the front air dam, illuminated scuff plates and the X styled 18" wheels.
I am missing the Dynamic Seats feature in my E55. This feature should be included for the future IS 350.