Ergonomic innovation is probably more critical to the higher standard of the new 10-speed S.T.I. levers than the added gearing. The narrower cradle-style perch welcomes the high-on-the-hood riding style and accommodates all sizes of hands. The shift internals borrow the robustness from our MTB technology which results in a smooth and effortless shift.
As an old geezer who cut my teeth on Huret derailleurs in the '70's and thought Campy and Superbe were the cat's meow, I have to say that I am amazed by the shifters. I have a new bike(summer 2010) with the 105 ten speed group, and the components are unbelievable in their smoothness. When you move the lever, even under heavy pedalling force, it shifts. I've grown much lazier in concentrating on precise timing of shifts simply because you don't need to pay attention. The close spacing of the 10 speed freewheel allows me to keep a respectable pace and *almost* keep up with the young studs. Have no experience with the durability of the parts since they're new to me, and I can't say how they compare to the rival SRAM or Campy setups. Eventually I'll put these bad boys on my throwback touring bike and my wife's bike.