Other than changing color availability from year to year, I think the only actual change was something on the passive restraint system in the 07 model year.
Also, I believe there was a difference in the way the 04's and 05's traction control or ESP is wired up. But only the 04's came with an automatic dimming rear view mirror.
The newer cars may come with the better designed "Fog Light" that doesn't lose it's deflector on the bulb, but I'm not sure.
Basically what you bought in 04, is pretty much what is now guaranteed for life in 2008.