I have a 94 accord and have the exact same problem. I've had the car for more than 2 years now, it just got a little worse than it was. From what i heard, most of the time it is the Vehicle Speed Sensor "VSS", which sends the speed reading to the TCU so it shifts in the right time. I've always wanted to change the VSS and see what happens, but never had the chance to. If you ever change it and it makes a difference, let me know so that i change mine too