Sram does make a "double-tap" thumb shifter. I use the double-tap road levers and I think that's fine. Since it was my first road lever experience and they seemed a good value I was pleased. Then later I borrowed a friend's bike that had Ultegra shifters with a thumb up and index down and it was immediately intuitive and smooth...that's after using the Sram Force for over a year. Going back the the Sram was harder after three months of Shimano than the other way. The X9 shifters seem like an even worse transition from real rapid-fire.
These things are still in unmounted, new condition and I plan to sell them that way. It may be fine for some people, but (like the double tap) it's less intuitive AND I'm well trained in another way. I once tried out a rapid-rise rear derailleur and I consistently shifted the wrong direction after months and months. I guess with all the hours of cycling over the past decade with consistent equipment my muscle memory is hard to rewire. From now on I'm staying away from Sram parts; I've just been burned too many times.