I lower the sense when I do the circles thingy, and higher then when I'm about to keep bhopping thru the map. You'll get used to it : )
Funny how u guys try silly ways to get speed, wats wrong wid getting speed with turning around in circles with your average sens :S And I bet you would fail most of the time while switching back sensitivity when you decide you wanna move forward.. Anyway, thats not really count has hacks because you are just keeping yourself busy switching around your mouse sensitivity..