I've never seen one in person, though I do have quite an affinity to them as I absolutely adore gypsy jazz ?
There's a really fantastic player named Jon Jorgenson who has a signature gypsy jazz style guitar made by a company called Saga, it's an eastern made one if memory serves me correctly - He in fact explains the differences between regular acoustics and gypsy acoustics in this video and also shows a few models out of their range:
All reviews and info I've found on them so far does paint them in a very positive light given the price, though the regular work still applies (setup etc).
This is basically the forum for gypsy jazz players, you can find a lot of info about affordable ones in here:
http://www.djangobooks.com/forum/
Also for what it's worth a deep bowl center hole placement style Ovation (but I mean a proper one) is pretty damn loud as well, definitely the loudest acoustics I've ever come across (and I have tried literally hundreds), owing to a couple of their structural differences, also a very midrange prominent acoustic owing to the bowl thing cause without having right angles inside like a normal acoustic it tends not to cancel out so much of that frequency range. They do a thing called a contour bowl now which is way more comforable to sit with, still slides a little though so I tend to end up sitting with a strap on regardless, my ovation is a side hole style one though, still very mid range dominant, they just don't project as much as the design is intended to help reduce feedback (I was playing in an electro swing style gypsy jazz band and even though the volume of my guitar was competing with full on club level low end and volume I literally never had a single feedback issue)
Just for good measure here's another Jorgenson video talking about his guitars again ?