They are really all the same. The '04 has the "crossfire" across the back set lower than the rest. I think that the glove box is a little smaller on the '07 & new cars. I can't think of anything else.

Hopefully you have enough opinions now to help you make a choice. FYI, my previous cars were a 911, 928, Lotus Esprit & Alfa Romeo Veloce Spider ..... I love this car so much more than any of those. They all had different things that may have been "better" than my XF but my little yellow roadster kicks their butts when it comes to sheer love of the drive. Plus this is the best car community out there! Of course if you aren't an amazing cool & quirky person then you won't fit in at all. That's for you to decide.