It'* possible that the previous thermostat was a lower temp thermostat, or the thermostat was defective.
The way it should work is the engine warms the coolant to 195*, at which point the thermostat opens, and the only means of temperature control is the thermostat closing again because the coolant is too cold, or heat dissipation to shed heat built up in the system. This is controlled through air flowing through the radiator, which is accomplished by the vehicle moving through the air, or by the computer flipping on the fans (now that I think about it, 212* sounds more correct) to shed some heat.
This puts optimum operating temperature range at 195*- 212*.
The only way to lower the operating range is to put in a cooler thermostat (180* is common), and to have your computer reprogrammed to switch the fans on at a lower temperature as well (190* I think), which would put the new operating range at 180*-190*.
Most believe that the non supercharged engines run better hotter. You are running exactly where you should be. As far as your concern with reaction time? The only time it would make a difference would be if you are overworking the engine, which you can react to in either case, or a failure of sorts, in which case you will not gain much more than a few seconds.
A side note, under normal circumstances, it takes a lot to run a 3800 hot, and usually the transmission would overheat first anyway. I don't know that you would notice a difference anyway, as the PCM always indicates 210* on the gauge when it is in the normal operating range.
In all honesty, drive it and enjoy it, and if the gauge starts climbing for no reason, then you have a problem, and need to track it down.