I've owned a bike with Tiagra 4600. This gear is as good as anyone needs. Because the shift cables run outside of the bar wrap, they feature smoother shifting. When Shimano put the cables under the bar tape, it introduced tight bends and extra friction. Plus the newer shifters eat cables regularly and when they do, it is a hassle to change them. I have used every generation of STI (and SRAM and Ergopower) shifters since the dawn of time, and Shimano 7700 and 7800 feature the smoothest and most precise shifting of the lot. 4600 is right up there as well, just a tad heavier than Dura-Ace.