I've never liked stem shifters because it seems like a very inconvenient position to me. Even with barcons you have to reach to the end of the handlebar.
For these reasons, I've gone with Shimano STI and SRAM double-tap . . . much better, pretty much right at my finger-tips all the time. My folder has Shimano Nexus (think twist grip) and that works fine too.
But stem shifters? No, I don't think so.
Rick / OCRR