I've just bought one of these units. The piezo start is great compared to the older Weller I had.
A problem though, is that the temperature adjustment range is much more limited than the older iron. The difference between lowest and highest setting is too small. The older iron could be adjusted right down so that the butane flowed inaudibly.
The Pro flows rather loudly and forcefully at the lowest setting and it is far too hot. It's more like a 50W iron than the 25W Weller advertises as its lowest level.
So I ask other owners of this iron: is this the case with yours?
I'm wondering if mine is defective or requires internal adjustment.