I love my 105 shifters, both 5600 and 5700 (broke one cable on the 5600 ones) but when I rode my buddies Ultegra equipped bike the noticeable difference is how much more solid the Ultegra is over the 105 (in regards to the snappyness of the shift and notice clunks of awesomeness). Ultegra will also have better resale, if that matters at all.