Fans are almost required equipment in all kegerators, IMHO.
One thing to get a more accurate representation of your keg (beer) temp is to tape your sensor to the keg itself, covered with a patch of insulation.
If using that sensor to control temps, however, I'd set your hysteresis (difference between on and off temps) as small as possible. This is because a full keg will take a long time to change temperature, while air or a small glass of water will change temps more rapidly. Those require more hysteresis in order to avoid short cycling the compressor.