I would not go back to down tube shifters again either. Any old bike I was to buy would be bought with the idea that the old stuff is coming off and the new stuff which would include Shimano STI's or the equivalent in Campy, SRAM or which brand components I'm installing.
No complication at all. Very little goes wrong with them. They might not last 40 years or more as have some of my older bikes with downtube shifters. But the safety aspect of not having to take my hand off the bars to shift is more than compelling to me for saying yes to STI's and their like brethren.
It's nice to be able to shift with both hands on the bars while sprinting up a winding hill.