I'm running 6700 shifters with an otherwise all Ultegra SL (6600) group. I agree that it was a worthwhile upgrade... for me. The ergonomics of the hoods are better for my hands. Others have expressed a preference for the 6600 hoods. In my experience front shifting is much better. Rear shifting is good, but not better than with 6600 shifters. Braking hasn't been way better either. However the brakes work fine even though the pull ratio is supposedly different. And yes, I find that the derailleur cables hidden beneath the bar tape is a plus.