I haven't got the Weller version but I've still got the one I used in the exchanges when I worked for BT. Can't remember the make. I still use it and find it very useful if I want to do some soldering outside where there is no electric for a normal iron.
Like John, I had the BT version and used it regularly when doing modelling demonstrations at exhibitions. It lasted for a couple of years until the valve finally gave up the ghost. As John says, good for when there is no power but I wouldn’t use one all the time. In my workshop I use an Antex 50W temperature controlled iron, they last for years.