In tests I've done, refraction is a killer that slows down render times a lot, but 2014 shows some improvement.

I just rendered a scene in 2014 (3 characters with SSS, wearing clothing, enclosed space with IDL, about 12 point lights and a bunch of ambient emitters, some reflective surfaces) and it felt quicker, so I rendered the same scene (same settings) in 2012, and boy was it quicker: it rendered in almost exactly half the time in 2014 as compared to 2012. When I upped the raytrace bounces to 4 (they were set at 1, which is what I needed for the scene originally), it was still faster than 2012 with 1 bounce.

2012: (1 raytrace bounce): 6:27

2014: (1 raytrace bounce): 3:31

2014: (4 bounces): 3:48.