I vote for taking delivery of your 08. I faced similar situation with my 04. Then decided I could keep waiting for one more year for a long time.
The way I calculate the deal is that I got a year of Boxstering, and the 05 did not blow me away. As you predicted for yourself, I liked some 05 changes and other not so much.
And spy shots aren't very helpful until the release date nears.
Go for the present!
