I have Starry Night Pro 6. I am reasonably happy with it, except for one thing. Every star, no matter what its apparent magnitude is, is displayed as a dot of the same size. I have tried different star display options (Spikey, Photographic etc.,), but the size of a given star is still the same, irrespective of its magnitude. I wish that Starry Night Pro will show Sirius, the brightest star in our sky, as a bigger dot than the Pole Star, which is much fainter.
I have other minor quibbles with Starry Night, but the above is the main one. If you can fix this, many of your customers will be very happy.