Today, I grabbed a thermistor and set about using one for the first time.
I threw a mega8 in the old breadboard, powered by my modified ATX supply. I connected an LCD for a readout, tied AREF to VCC with a .1uF cap to ground. I used a 150k thermistor in series with an 80.6k resistor as part of a divider, and used another 80.6k resistor in series to the ADC pin.
Doing the ADC to temp conversion code took me a little bit, but it worked on the first try. My first impression was that the thermistor (a moleded disc) is VERY fast to react to the environment - just breathing on it with one long breath is enough to watch the readout go up by two degrees.
The second impression was how stable the ADC readout was on a traditionally noisy source (a breadboard), and without the LC filter. In a relatively stable temperature, the ADC readout would only vary by +/- 1 LSB, *occasionally* going +/- 2 LSB. I had expected more of a fluctuation than that.
My third impression was on the self-heating of the thermistor - after five or so minutes of running, the temp readout would be 2 or three degrees above ambient. With the seemingly low thermal resistance from the first impression, I hadn't expected the 20 uA going through the thermistor to make much of a difference. And, thinking about it, it shouldn't. I'll have to double-check readings tomorrow.