Thermal sighting on a M1 is awesome. You can read the ingredients on a can of coke sitting on top of a turret 200 meters away. The problem with it is heat. You have got to run the thermal imaging cool or it'll just stop working. This has nothing to do with the outside temperature, rather, the inside temperature. Right now it shouldn't be that big of a deal, but once that tank reaches temps of around 90 on the inside, it'll start failing unless you can cool it down.
Most tankers prefer the thermal to the the daylight simply because the targets are easier to find. Look at a picture of an M1. On the top you'll see a small box right in front of the commanders hatch. That's the dog house. The two flaps in front close. One side is the thermal scope, the other is the daylight scope. You'll probably see them with both doors open though. A good indication the gunner is using thermal.