I have the single action mod from the CZ custom shop. To be honest, it was a disappointment -- the result is a long do-nothing pretravel followed by the single action pull, in a "two stage" setup. Using the adjustments to correct this, the gun cannot reset the trigger for the next shot; the long pull is *required* unless something else inside the gun is modified to work. So, really, its virtually identical to a cocked shot on the standard DA/SA.
My wife loves it, I found it to be "meh".
Also, the cz shop really messed up my gun. On the phone, I ordered a left handed rami -- it would get the trigger job, a left hand mag release, and an ambi safety. The delivered gun: right hand safety, left hand mag release, and crappy trigger. Called them back and they explain "no can do" --- the ambi safety wont go in the metal gun and the trigger job won't go in the plastic gun or something like that... I was NOT happy but I kind of let it slide because they did a 125% awesome job on my wife's purchase.