My practical experience with the MaxBotix sensor is this: it will mostly return values between 12 and 254 when connected to Arduino, correlating to inches. However, there will be occasional spikes of higher values, up to 500+. Strangely, these spikes seem to occur when the sensor is pointed towards a highly (audio) reflective surface at close range.
You can use the PWM or serial outputs on the MaxBotix as well, though these correlate quite closely with the analog output. The PWM is excellent when using multiple MaxBotix units, as you can chain several units together.
Thank you very much. Also, what do you think about using two sensors and then comparing them in order to get an averaged value? Would the PWM just be easier and more efficient method?