The bigger engine in the TL-S made a big difference to me. I was set to get a G35 until I drove the S model. Great quality, thrilling to drive. I LOVE this car. Only thing I don't like is the lip spoiler in the S. In fact, my wife loved it so much we got her a base model TL two weeks later!
Handling is phenomenal. It's so fun to drive. Nice options and features. Love the bluetooth and the voice recognition.