For the most part, I'm like you watching the viscosity over the probe when working with the microwave... (I want it to pour like heavy whipping cream)... even with light colors, which is over half of what I shoot. This is something experience will show us, but I don't recommend it for beginners until they get a true feel for things.
On occasion, I will go with my hot plate and pot for certain batches and there I religiously use a thermometer (even though I marked my dial as to where I get the correct temps are) because of the slow response time when adding more (cold) plastic and trying to maintain temps where I want them. It is just too easy to overheat, especially if the slightest bit distracted, because it doesn't shut off like the microwave.