I used to run a Allteck advantage pro with a heater in tank.
Ive just bought a eclipse, it doesn't have a heater, and i have found that i don't need one!
using M/S and doing things the right way. having heat makes no difference, as nick mentioned, most pile is heat set, i for one would not want to use "steam"
The power of the eclipse works, i get cleaner carpets and my drying times are great, with the eclipse.
When i started cleaning carpets(many yrs ago) my machine didn't have heat,none of them did! and we didn't give heat a second thought!
I find tap water to be ample, and by not having to wait for the machine to heat up, my productivity has increased.
I do believe the heat issue is SIMULA to the early thinking about m/s, in so far as "Ive always done it this way" so it is the right way, we just need to open our minds and try things a different way every now and again, who would have used chewing gum remover to clean of Lilly pollen, if we didn't try different things