Nvidia seems to have gained the most from 28nm, because their uarch was already pretty good with Fermi, it was just improved greatly with the changes they made for Kepler when it came to perf/w.
Titan pretty much doubled the gap in performance difference between last gens two top cards for each side, and it did it while decreasing power from ~245w to ~206w.
Prices though have been awful for 28nm.