The only drawback I can see to a heater like this is the problem our dog would have moving around the van while the heater's on and the dust cover is off. It would be a bit like a cattle grid as LEF said.
Big dog - small van, I'm sure she would manage but it would just make her life a bit more difficult and as she's so brilliant in the van anyway I wouldn't feel comfortable reducing her availiable floor space unless I had to. The propex works fine as it is but I'm just attracted to the relative simplicity of this type of heater. I prefer simplicity and elegance to solve problems.
heres a pic of mine .. im chuffed as i painted it 5 yrs ago with enamel .... and its better than paras....