I traded in a 2003 525i to buy the 2005 545i. While it has taken me a little while to get used to the new styling, it has taken no time at all to get used to the sheer driving power and pleasure of the 545i. Über-responsive and just terrific fun to drive, I am very happy with my decision.
The new navigation system takes the fear out of touring.
Look again at the internal styling. I really think the 2003 version was warmer, particularly with more use of wood in the doors.