Has anyone considered the
Daimer Super Max 6000? It's a propane heated high pressure (750 psi) steamer. It'll spray cold water, hot water or wet steam. The video on Daimer's website states a wet steam is preferable to dry steam when using it on exterior surfaces. The additional water content acts as the lubricating agent, thus preventing scratches when washing a car (their words, not mine).
The Super Max line made in the good ole' USA and also costs around $5200, which puts it in the same class as the South Korean Optima steamer. The Optima is diesel heated and is ready to go in 2 minutes; the Super Max is ready in as few as 30 seconds.
The Optima's operating pressure is around 120 psi and can be used with two spray nozzles so one can work the exterior while the other person works the interior. I've heard Renny Doyle say that high pressure steamers are not necessary as they can cause damage where lower pressure steamers don't. Is 750+ psi really necessary?
FWIW -- I think the NB2300 steamer is around $3500. I find this unit very interesting.
I like the idea of using steam for total detailing. Very little runoff, doesn't use a lot of water, versatile and effective. Eventually I'll migrate towards a Super Max/Optima type system and go *green* (like the folding kind, eh?).