I think your upgrades to Dura Ace at the price you got is very wise. I've recently done the same thing (some parts were slightly used) and while the difference in performance is not extreme, I think it is noticeable. The shifting, cranking, braking, etc is just a little nicer. I enjoy the benefits of the slightly lower weight as well. If you're going to spend 5-6 hours on a bike, climb mountains, ride 5000-10000 miles a year and push yourself to the limits, why limit yourself????
You certainly get my vote!!
By the way, I picked up another interesting tidbit that is sure to spark debate but it is around chains, one of my local buds who is really on top of the equipment swears by using Campy chains on Shimano/DuraAce components. He has lots of experience that would indicate that the Campy chains last longer and the pins are easier to use. He sells all types of equipment and that is what he rides........When my next SRAM chain wears out I'll probably give it a try.