DL'd it, played with it, made some backgrounds.
Writing a review for those interested.
Ok, here we go:
THE GOOD: It is a
very nice app, which allows for some amazing skybox graphics. The quality of those graphics is, of course, proportional to the time spent working on them ( NO!
Really? 
), with the really realistic and awe-inspiring ones probably requiring a few days' work. Since I didn't have a few days, I just made a few mediocre skyboxes, but I can see what Peterson made with a mere 10 layers and I can only imagine what is possible if you get your mind to it.
THE BAD: Sadly, the app has some problems, too, which seriously limit its usefulness.
Procedural generation is all fine and dandy if you need some quick and dirty nebulae or starfields, but it has its drawbacks too. For one, it is exactly that:
procedural. That means that there is absolutely no way you can fine-tune the shape of those pretty nebulae, the position of those stars, or the location of any other billboard graphics you use.
For example: there is
no way one can create a galaxy-plane effect (the 'Milky-Way-Band' one can see in the Earth night sky). There is
no way you can place a green nebula next to a red one, but NOT inside it, but there on the side, with those nice yellow stars and the pink polka dots or whatever billboards you use.
TL;DR: A very nice app, that, unfortunately, limits itself to the making of basic skyboxes;
amazing skyboxes, but basic nonetheless. What you
can do is slap up a good starfield or faint nebula, and then go to work on it with another 3d app, or image editing software of your choice, to add those necessary planets/ galaxies/ whatever.
All in all, a 3 out of 5; one point off for lack of all but very basic tutorials/documentation and another point off for the -more important- lack of billboard placement options.
Cheers, and good spacescaping.
