Hi Steve,
I use one with a truckmount system and it works ok for me. Mine is used any where between 50 psi to 250 depending on what I am cleaning.
What you ought to think about is it is the amount of water you may use,with the truckmount its not a problem but it could be with a portable machine.
Its good to have a constant temperature at the slot, again as with most hand tools you have to be careful not to have the temp to high.
Regards Tony Harrison