Define "sensitivity." Do you mean "accuracy" or "repeatability"? "Lag"?
The main cause of error with thermistors, IMO, would be that the R vs T curve is non-linear, so most of the error would be calculating the temperature for a given R.
As I've heard it said, most temperature measurement devices are not super-accurate as it is usually not necessary to get super-accurate temperature measurements.
You could increase your performance by making sure the thermistor leads are short, use precision resistors in your voltage divider, make sure your A to D is ratiometric, maybe use a low pass filter.
j.