Well it can take up to 30 seconds to acquire the satellites on start up, but if you add consistent power to a certain harness it will keep your last know gps position so the acquisition is faster. I didnt wire that feature in because I never jump in my car, fire it up and take off. For responsiveness Id wager sensor or mechanical is more reliable for real time speed input. But we are talking milliseconds here, my eyes cant register the difference. I dont notice any sort of input lag on the SpeedHut. I stab the throttle and the speedo moves, all the way up so far 119mph when I ran out of gearing. Its never jerked or lagged out and works at low speeds, something my mechincal speedo never did. I can change my final gear, rear gear or tire height and not worry about my speedo being off. The only issue I can see the SpeedHut running into is if you live in an area that has extremely poor gps signal.
SpeedHuts are good to go.