I have used it and was not very happy with the results. I used my tried and true HVLP turbine system, that has done about 12 other, more successful paint jobs. I bought the needle set recommended by Stewart, and tried to utilize their advice as much as possible. Just didn't turn out very good.
I won't use it again, because I can get a good job with other products. If you use it, and I'm not saying "don't", buy the Finishline III or comparable compressed air gun like they recommend. That's the only thing I can think of to do differently for a better result.