I use bar end shifters. They are harder to use than STI levers. However, the main advantage is simplicity. I have had bar end shifters set in friction mode for the past 3200 miles and I have not had to adjust anything during that time. STI levers are simple, but they require regular adjustment of cable tension and derailluer limit screws to keep working properly. In addition, if your STI lever breaks, you might as well buy a new bike given how expensive it is. I realize that I am in the extreme minority when it comes to bike buying customers, but I prefer friction shifting. Bar end shifters work well enough, are cheap, and don't require frequent adjustment.