sprint_veloce

That's pretty much on the money. If the temp gets to 75° quickly from a cold start then your thermostat is working perfectly. If it struggles away to 50 or 60° then there's a problem. The gauge itself isn't necessarily a very accurate instrument, so don't take too much notice of the actual numbers. More the pattern of behaviour.

And if you're worried that your car's running too hot bear in mind that the coolant won't boil until about 120°, so you're unlikely to do any harm below that. The warning light should come on at about 110-115° - that's when you need to stop and investigate.