>Open element sensors and low-mass sensors should be fast.

Well, you do not say just how fast you need them to be, but I would have 
thought the fastest would be the tiny bead thermistor types would be ideal, 
and well suited to the temp range you mention. One like the YSI 4400x series 
is what I am considering here, although they may need some small 
linearization for best results.

>But I'm sure I am missing a lot of other possibilities here.

Personally if you can stand the cost I like the Analog Devices AD590 device. 
One of the package options is a lowish mass ceramic case that seems to have 
reasonable thermal response times. Sensitivity is 1uA/K, and they are 
linear, operating over -55 to 150C. Use a 10k resistor to ground, and a 
supply high enough to have at least 5V across the sensor, and you have a DC 
voltage just right for putting into the ADC pin on a micro, although for 
best accuracy you need to offset the low side of the reference voltage.

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