They're very handy. It starts and lets the car run for 10 minutes. You can re-start it with the remote and it will run another 10 minutes. Then, you MUST use a key to start after which, because the remote resets itself. What else is good is that it works with GM's anti-theft system. If someone breaks in the car while it's running, they can't take it out of gear or do anything without the key in the ignition.
Also, I've learned that GM is coming out with another remote starter for aftermarket applications that not only will increase the area up to a 1/4 mile, but also tell you the tire pressure of your vehicle as well.