Replaced my 2003 Avalon with a 2007. Engine power and responsiveness much better with the 07. The power lock system is much more user friendly than the 03. I always felt I couldn't get out of the 03 (doors would lock) and with the remote lock/unlock always had to hurry before auto relock. The window washer is outstanding on the 07, that last swipe makes all the difference. I didn't go with the JBL (had it on the 03) and really can't tell a difference. Absolutely love the car.
3.5 litre engine, turning radius seems shorter on the 07.
I agree on eliminating the cassette and subbing an iPod connection.