To be honest, I have no idea at all how well the forge will perform or for how long. I get the impression that it is a reasonable starter forge and that it should be ok until the purchaser has worked out what direction their interests are taking and they can then decide what characteristics they want in their second forge.
For most people, their first car will not be a forever car and they understand this. Learning smithing (or any one of a number of things: fishing, hunting, golf, etc) and learning to drive are not entirely dissimilar in this respect. For some reason many people struggle to see this.
The Devil Forge burners are much more controllable than many people seem to realise. I bought one to play with a while back. The screwed choke adjustment means that you have a very wide range of flame temperatures available. Maximum flame temperature is achieved with the choke fully open and the flame temperature can be reduced by choking down. Between the pressure adjustment and the choke adjustment, you should be able to get welding, forging and even HT temperatures. For HT temperatures, you’ll probably need to reduce the forge openings. If you don’t, there is a high probability that air will flow in at the bottom by convection and cause the temperature to increase. Some experimentation is likely to be beneficial.
It is worth noting that Devil Forge also sell a more expensive version of their burner which has a sliding choke instead of the screwed choke. I would expect this to give poorer control (though I could be wrong).