I know my detector works well, when a policeman is driving around with the gun on it will tell me he's coming LONG before I see him. Even instant on (hold, why would it be called that, "instant on" is much more descriptive :P ) it will pick up pretty far away. It has definitely saved me many times, but you have to use them right.

I don't hesitate to recommend a valentine to anyone who is in the market for a good detector. Would be cool to hear from anyone who has better knowledge of how they work though.

And yeah, speeding through a school zone is about the dumbest thing you can do.