On the topic of the cop sitting in the corner, when I lived in Colorado I read a quote from a cop who said they didn't run many speed traps in the mountains because they didn't want this kind of thing to happen.
If the cop has eyes on you before (or while) you hit the brakes in a speed trap situation like that you are basically screwed. Even without radar evidence the cop can give you a ticket based on their guestimate. I learned this after I started believing my radar detector/great brakes gave me an edge. Not like you can really tell a judge that he should believe your word over an officers if you drive a sports car and/or have past speeding offenses.
Edit: Not saying you shouldn't hit the brakes though. I'm sure an officer would rather see you have the good sense to slow down in response to their presence then acting like you don't care... or worse doing the opposite and trying to run. Better to just accept that you are caught and be calm about it. I see that bikers reaction as an example of speeding without being able to accept the consequences. It just makes it worse.