if your talented at Oxy welding sheet metal together then a Henrob torch is a good idea particularly if your interested in hammer-welding butted joints.
not for the amateur but with the right expertise and practice you can perform practically invisible welds, in the hands of the right operator its like magic has been performed.
checkout streetneat.com.au the gentleman who owns this panelshop is a big user of a henrob torch and his site shows how he utilises it.
unless your doing high-end restoration work for high paying customers you wouldnt normally go to the trouble of learning a whole new artform when a mig welder should take care of majority of requirements on a mini body.
then again.....you may get a kick out of playing with it

its amazing to see what its capable of.