Well, they say its hot water, but I don't think they specify an actual temperature. The good thing is that it's not an immersion heater but an inline, so it heats the water quickly as it passes through the heater and as long as you don't leave too much time between trigger pulls, the temperature will stay constant. I hardly ever use the heater TBH, only on real greasy carpets. Remember, the right chemical for the job, and good agitation and technique is more important than a bit of extra heat. PLUS you have 500 psi to power through the dirt so I wouldn't worry too much about the heat.
I think it's an adequate machine for most jobs, a powerful pump and 2X 3 stage vacs plus wonderwand means low drying times. I'd imagine a truckmount would be overkill on most jobs, just gets the job done quicker. You got a good bit of kit, use it right and the sky is the limit my friend

You can always have a chat to the people you got it from, how long have you had the machine?
PS I read that too hot water can damage pump seals so I wouldn't have it much hotter than 40 c in the tank.