I've tried everything in the Shimano line up from the 2300/Sora set up to Ultegra and the 105 is without a doubt the best price/performance ratio. I've owned it on 4 different bikes and it is rock solid with crisp shifting. I personally don't like the ergonomics of the new 5700 shifters as the 5600 supported my hands better. The Ultegra is a bit more polished and the shifts feel slightly more buttery but not worth the major price difference unless on sale.
(Posted on 12/03/2012)