I think the sign of a good truckmount is if the owner keeps it for a long period of time, if you are thinking of buying a Boxxer then speak to someone who has owned it for a long time and not got rid of it as soon as possible,
the same goes for Ace machines from Chemspec, find someone who has owned it for years,
what you need is unbiased points of view, which will be hard to find.
my unbiased opinion is to buy a Prochem machine. over priced but I've never heard a bad thing said about them, I have heard bad things about every other truckmount sold in the UK ( apart from the blueline range which haven't been here long enough to gain a bad or a good reputation)
Mike