I upgraded from the older ultegra 10-speed shifters to this one. The 11-speed works well. I installed it and the derailleur myself and worked like a charm. You can download the installation manual from Shimano's web site, which was helpful.
I've ridden a lot of different setups over the years. I was beginning to think the only way to get amazing shifting was to go electronic.
I bought these out, slightly begrudgingly, out of necessity.
WOW. They're amazing. Paired with the Ultra Slick cables and housing and the new Front D, they are the best shifting I've ever experienced.