I have a non-branded IR and also a thermocouple.
I used a Fluke IR on a marine application, they are quite useful BUT- The Fluke's  operators manual describes materials that their IR cant get a good reading from. That  essentially includes surfaces that reflect, like mirrors or polished or painted steel surfaces. There were many materials.
Any other branded IR will do just as the Fluke does. They are great for things like rubber hoses (coolant) or exhaust pipes. I have deduced  yet, not directly read it... I mean The Fluke operators manual desribes the limitations of the tool, naming like materials including the mirrored or painted but did not elaborate.
The laser is not the heat sensor, it is only used as a reference point for eyesight of the user. You ought have the unit placed close to what is being measured.
I saw recently that a painted surface, it was a cylinder head, gave consistent readings, if not accurate as Fluke said. Fluke does not  describe what happened if you measured those materials so I INFERRED that to mean there is a problem with magnification of the heat as well as reflection; it is measuring infra red waves, light is  'electromagnetic frequency' in the schoolbooks.
Since we are dealing with frequencies, and light and heat are reflected by the polished surface; readings are skewed by the reflection of the heat.
A rusty exhaust is not reflecting much heat so you are measuring only what you are pointing at, essentially.
You could use that tool you are buying to measure catalyst reaction times... perhaps if you had known good catalyst readings to start out with, for comparing... Here is one damned thing... I know there is a distinct measurable temperature difference bewteen a lean burning cylinder and a rich one. Large diesels commonly did have a pyrometer located at every exhaust port from the cylinder, used to judge the condition of the injectors.  Cylinder temperatures could be quite useful in studying misfire problems. If we can eliminate air/fuel ratio as the cause of misfire then the rest is icing on the cake.
Lean misfires will commonly burn hot and spark ignition failures are the opposite; the fresh injected fuel and air dont burn and they cool the cylinder walls instead of dry it out... how dumb is that for %^&*()'$ sake?
Pardon me, I mean there is an easy way to determine if a misfire is fuel caused or electrical caused.
MAN! A thermistor/pyrometer plug could be screwed into the exhaust at every cylinder... I suppose the OEM are depressed that you'd need to wire the exhaust manifold. What a pain.
        The temperature differences are profoundly measurable, compared to the existing phenomenon. . Not having that kind of self diagnosis in the ECM is liked being stopped at a stop sign and waiting for it to say GO!
MAN!
  Hey, I hereby claim the that I thought of it first.
Your new tool is going to work wonders, Mr. Jarvis.

Fisher my thougts for use of these tools would be more a long the line of heating and air conditioning.  The three sensor would be adequate for looking at heater core inlet and outlet temp and vent temp at the same time.  The 8 ch one could also look at the radiator inlet, outlet, thermostat  and still have two more sensors available for use.

For ac it would be similar deal the inlet and outlet of the evap and vent temp with the 3 ch and the other would do that plus the condensor inlet outlet.

Misfire use is a possiblity but the newer cars cat. code long before the cat would have not heat increase.

Sam