well yeah, like i said the lag is due to the computer loading the updated profile in the razer software. the actual mouse is fine. the imperator might have a slightly different software set. there really isnt too much you can do about it unless razer decides to update their drivers to account for this.
i always keep the dpi between 900-1200 and leave it static. there is little difference when zooming in to snipe than shooting far off targets non-zoomed. i can't fathom trying to play with 3500+ dpi as some people swear by. personal preference, but i find it far superior in FPS.
having a cloth mousepad can definitely help as it will eliminate any mouse drag which might cause micro-movements of the mouse on a higher dpi. that way there is no need to change the mouse dpi in order to make your aiming more accurate.