I'm finding this thread interesting because I've never used an electric impact wrench and often wondered if they're any good. Sounds like they're okay for limited applications.
Re: the torque sticks, I don't trust them, and I agree that if you let the gun keep hammering on them you'll overtorque the fastener. They work by using a spring steel alloy made and treated to let loose like a spring at a specific torque. But they don't prevent the operator from continuing to twist, even with the metal having let go. I just don't trust them.
For many applications, especially where torque is critical, I prefer a "beam type" torque wrench. I like them 'cause I can see exactly what's happening. For some applications I use a "click-stop". I realize that they're as susceptible to misuse as the torque sticks, but for changing a wheel you can feel confident even on a cold, dark, rainy night with no streetlights around. Can't do that with a beam-type torque wrench... too easy to misread in low-light situations. I keep a click-stop with a deep socket in my trunk preset to the proper lug nut torque. I'm the only driver of the car, so I know it'll always be there and properly set when I get a flat tire.
A lot of this is actually just preference. If you're using any type of torque wrenches, you're already using far better practices than a whole lot of people.