Recently bought the IS 350 and sold my Audi A8 as it had 128,000 miles. It was a big change, but each day I like the car more as I learn more about it and drive it more. To me it seems like a luxury go cart! It is very responsive both in steering and acceleration. The front seats are surprisingly comfortable for such a small car and the back seats are very well thought out except for the leg room is a little shy if you are over 6 ft and the front seat is all the way back. I like the no key entry and start feature and the nav system which I am trying to learn. Also like the manual automatic shift feature. Not much to dislike so far. Probably will keep the car for quite a while.
Air conditioned/heated comfortable seats. Quickness/acceleration. Also the "no key" system.
Would like to hear less tire noise. Shuts out almost all traffic noise, but tire noise still gets through.