I have two Surefires with clickies. One E2DL that is pretty new - the original clicky works just fine and also the Z61 I recently got for it.
But my G2X pro has a little glitchy switch, I have even replaced it once but it behaves the same way.
Some mode skipping, not a big problem but I wouldn't call it "super reliable"
My Surefire twisties (6P, C2) feels and works great.
I also have some other lights (Fenix, EagleTac and others) and I have actually never had a clicky fail more than a loose retaining ring making the light not work properly.
Of course, my lights doesn't get that much use that I know some of you other guys give your lights.