Anyone use a PWM cooling fan controller?

[GS guy]

I'd jump on that ryans88gt, if one were made for the operating range I'm looking for - and could monitor the intake air stream temperature directly. I see the Hayden unit you referenced will got down to 120F - the lowest I've seen for this type of controller. Most only go down to 150F - a temperature I'm trying to keep my intake charge well below! If I could get it down to 100F I'd probably go for it (although the Hayden units don't have the most stellar reputation for reliability....).
Also these units are made to monitor water temperature - many use an external probe that "monitors" the metal temperature outside the radiator. At least the Hayden has an optional 1/8NPT probe that can be inserted directly into the water stream. Not sure how responsive this would be in an air stream? Especially the rapidly changing conditions inside a boosted intake system.

The other options is to run a high-watt resistor in series with the low-speed circuit, dumping power and turning it into heat while providing a lower fan speed. The little PWM unit doesn't consume power that way - only what the fan is using at the lower speed setting. I'm running a tiny battery, so sensitive to excessive current drain with too many electrical devices.

I've already got outputs to turn on/off a fan "built-in" to my megasquirt - plus I can control this with many different user-selectable parameters. I see no reason not to use 'em!
Jeff