They are a bit of fun in the right place but you need a loan for the fuel. I followed one into Norseman in December and was talking to him while re fueled. The thing had 2 x 85 litre tanks in it and the guy reckons he still couldn't get 1000 ks out of a complete fill.
Obviously aerodynamics are a non existent thing in these things but even so I'm glad my Nav wasn't using 170 litres every 1000 ks, although I'm sure these things go a little bit further off road than my Nav too.
I have been in a 4X4 and a 6X6 version when I was in Army cadets baout 12 years ago, they are great, only thing is they only do about 90km/h, but they will do it just about everywhere.