The finer details of its operation are a bit of a mystery and as others have said it could probably benefit from some calibration. I used low temperature solder paste and had success with my first (and so far only) board - there did not appear to be any dry joints and the solder flowed well, components didn't fry. I think it is trying to follow some kind of sensible curve when aiming for the set temperature.
In all a good tool for the hobbyist and occasional user, reasonably priced for a reliable service from Europe. This is my first experience with hot-pate SMD soldering and it went easily and successfully.