The experience is much better than the vanishing point filter in PhotoShop. No more guesswork to draw the guidelines, no more fiddling and copying/pasting to move your artwork. Everything is ultra-precise and with total control for the designer.
A few drawbacks though for the casual designer. You need to have a version of Adobe Illustrator installed on your machine (and more importantly, know the basics of how to work with it). Secondly, the service charges a subscription model that works if you need to use a lot of these compositions, but is not economical for infrequent use. And finally, the library of surface images is smaller than you would find on regular stock image sites.
All in all a good service, and as a professional designer, I might give it a try.