I have tested render speed in BMW scene. With vanilla Blender it was 209 seconds, with E-Cycles it is down to 119 seconds (1.75x faster).
Classroom - 627 seconds with vanilla Blender and 446 seconds with E-Cycles (1.4x faster).
Impressive speed-ups. For rendering I have used CPU and overclocked GTX 680 (1200 MHz GPU and 7100 MHz memory).
Also, support is good, all issues (specific to E-Cycles build) I have found and reported were quickly fixed.