The folks at Art's Cyclery offered this and their picks for "the best value Shimano road components":

Rear Derailleur: 105 5800
Front Derailleur: Dura Ace 9000
Shifters/Brake Levers: Dura Ace 9001 or 105 5800 depending on budget
Cassette: Ultegra 6800
Chain: Ultegra 6800
Crankset: Ultegra 6800
Brakeset: 105 5800

So when I bought a new groupset I went all Ultegra except for shifters, where I coughed up the extra $100 for DA.

Art's Cyclery Blog » Shimano Road Components ? Where to Spend Your Money