If anyone is looking for a very fast, cheap, maintance-free color printer, please have the folks at Tektronics make you a test print. If your looking for a digital proofing system that accuratly simulates a large range of press conditions, visit a shop that operates a Digital Waterproof. DuPont will then be working towards converting their aforementioned CV system to work digitally. I hear good things about the Dupont system but you have to take it with a grain of salt. If you are creating a duotone with PMS xxx you may very well be the first person who has ever tried to emulate that particular color with the proofing system.
All custom inks have certain foibles that one learns how to cope with the hard way.
By all means use such a system as being better than nothing but don't expect the accuracy of a CMYK proofing method that has been tested on millions of jobs. Quality continues to improve remarkably, as Jeff points out. A quantity of 100-400 puts something like Xeikon or Chromapress in the ballpark. They style themselves as digital presses but have a lot in common with color copying technology. Indigo, which uses a liquid toner technology, should also be competitive.