Although I drive the diesel, which didn't get the exterior changes, I have so far noticed that the 2005 seems to be better screwed together and quieter than the 2004 model(also duesel) I traded in.
Thing I miss most is the clock, keep looking for it on the roof, where IT SHOULD BE.!! Other changes like the larger rear-view mirror and extra lighting in the doors are less significant and wouldn't sway me one way or another.
If you can find a used example with a spec that you want then I personally would go for a used mini, but and it's a big but, having a car custom specced for you is a joy to collect from the dealer.
Just my 2 pennies worth.