I have beaten 2 of these (not even won in court...it was thrown out when I went to the initial hearing to get a court date). And I have seen more than 4 or 5 get tossed by other people when I went in. There is NO WAY the cop can measure your acceleration not to mention that there is NO RULE for what proper acceleration speed is! At least NOT in California books! As long as you don't chirp your tires, leave smoke or go past the speed limit, you are FINE. Technically, you can gun it up to 40mph if the speed limit is 40mph all day long ;) Wonder what they'd do though if you raced someone up to 40mph...LOL.
Again, that's in Cali...I can't imagine it being much different elsewhere.