After driving a 2006 TL for several months and purchasing a 2007 base model, here is my take on the differences. The 2007 is a little better overall. Its suspension absorbs bumps better than before while still maintaining its sportiness and handling. It's quieter on the highway and its seats are more comfortable (softer) - especially on longer rides. From the front, the separate fog lights, chrome-like strip along the bottom and integrated blikers in the side mirrors, give the car a more elegant look. The sporty body style, sporty handling and very comfortable ride made it a good choice for me. Notes: No squeaks or rattles, the new transmission is now derived from the RL's tranny.
Bluetooth phone, DVD audio system, ride comfort, an MP3 jack, blinkers on side mirrors, day time running lights, excellent crash results, body style and interior design. P.S. The ride comfort reminds me of my base 2003 TL (which I traded in) but with much more sportiness, power and agility.
SH-AWD, ability to control MP3 player from the steering wheel, better looking rims (small nitpick) and more interior color options with each exterior style (or at least with the more popular exterior colors).