The fuel burn target was a 20 percent improvement over the 767 on a 3000 mile flight. The improvement actually gets better then that at longer ranges up to 6000 miles. They have met that target. In addition the AvWeek test pilot described the aircraft as one of the best flying airliners ever. He really liked how the aircraft is designed to keep the pilot in the loop on everything that is happening. Here is his summary.

"The 787 is indeed the nicest handling and most docile handling Boeing jetliner I've yet flown. Enhancements in the companies FBW flight-control system increase safety margins and make the aircraft impressively pleasant to hand fly.
The aircraft can be flown with equal ability from either seat because the left and right sides have the same access to displays, controls and tools, including left and right HUD's, EFB's and steering tillers. Situational awareness and crew resource management are top notch because of moving and interconnected control yokes and rudder pedals, along with back-driven throttles and speed brake handle.
Admittedly, the aircraft entered service three years later then planned. But, judging on performance, it was worth the wait."

Avweek is noted for unbiased reviews and I have read others from this test pilot that were far less flattering for other jets.