If there's something I don't understand I'm open to enlightenment. Every time a thread that involves stitching arises someone mentions the requirement for "perfect levelling" when shooting. This puzzles me. When stitching, every pixel is remapped. In the case of the application I've been using for years, PTGUI, there's the capacity to adjust the geometry of the stitched composite image - including, obviously, the horizontal component: ie levelling. I'd assume all other stitching applications have the same functionality. So what's all the concern, again, with levelling when shooting?
As for the product itself, it looks like yet another solution looking for a problem.
Roy
Bart answered this well, but I'll add a little bit. For single-row panos like this one (just a test shot BTW) if the rotation isn't level, you end up with a stitched set of shots that's at an angle, or in an arc depending on what isn't level. The problem with that is the shot then has to be cropped and you end up cutting off the top and the bottom. Sometimes this is severe to the point where the shot is unusable because key parts of the composition are cut off from the shot. Obviously you always want to leave some room at the top and bottom of any pano for cropping, but sometimes you don't have that luxury, particularly with real estate/architectural work where your back is against the wall.
Also on the last statement - if you've ever tried to use a big telephoto lens (i.e. 200mm f/2 or larger) on a ballhead, you probably understand why it doesn't work well and can tip over your tripod. Additionally, when you're tracking birds in flight or other animals, cars, etc. by panning the big lens only to end up with a crooked horizon, you would also see a benefit here. The solution is a gimbal, but that ends up being bulky & heavy, plus it's not practical for use without collared lenses and simple landscape shots. So before Uniqball, the solution, if you wanted to shoot landscapes and wildlife, for example, was to bring both a gimbal and a ballhead, which was a real pain. The Uniqball isn't perfect, but it's an extremely good compromise that replaces a leveling base, gimbal, and ballhead all at once.
So if you just shoot with big lenses, a gimbal (with leveling base) is best, and if you just shoot landscapes and general purpose stuff, a ballhead and going to work very well. If you want to shoot both, however, the Uniqball is definitely a great solution.