I bought two K1s. The one I gave my wife works very well. The one I use has a problem with a sticky fire button. I've had it apart, twice already, and treated it to some gentle filing on the flange of the fire button and dry silicone lube, but it still sticks. The other thing that bothers me about the fire button on it is that the contact area for the micro switch on the board just seems too darn small, like it will, eventually, puncture the rubber membrane of the switch. Next time I take it apart I'm going to modify that as well, JB weld and a file will do the trick, but it'll take the mod out of rotation for at least a full day and I use it every day.