Brought one of these $10 thermometers to go with my $15 Yihua 936 clone soldering stations.
Personally I don't have $406 AUD spare to buy the real thing from Hakko as I am not in business or would ever feel the need to buy one at that price.
If these fakes were branded or designed slightly different I would have gone for that instead, never really liked blue Hakko stuff anyway.
How well does it work? Well it's quick to pickup temperature changes, almost instantly.
It's surprisingly good at detecting room temperature. Faster and more reliable it seems than most household thermometers.
I've not tried to check the calibration properly but it's close enough for me. It does have reproducible accuracy and of course you can calibrate it.
If I remember correctly I measured up to about 350C/572F. Others reported they measured freezing temp fine with ice.
PCB has good workmanship and soldering is fine, a very slight splash of something on the PCB but it doesn't affect operation. If I could be bothered I'd clean it up with IPA.
Be warned if you get one there is a trick to putting the spring loaded arm back in, so pull apart at your own risk.
Again this is a fake, don't buy one of these for hundreds thinking you're getting the real thing.