I've just finished painting the hull of a Fletcher using Gators 3x/9d masks. I sprayed the whole hull Haze Gray, masked and pulled the Ocean Gray panels, painted then remasked & pulled the black panels, and painted. It was my first attempt using the product. I ran into two problems.
1) Getting the off the backing in one (hull) piece and getting it initially aligned and rubbed down. There are some areas in the vinyl mask which were not completely cut through. Aligning the bottom or top and bow. Once they were aligned -- things generally lined up. Perhaps clear masks would help.
2) Misalignment on some panels which were sprayed the second color and reapplied. I have some narrow gaps & holidays which I've had to mask & repaint individually.
I code marked the color for each panel before removing the mask from the backing. That helped identifying which panel to pull. On hindsight I would also draw an alignment tic across adjacent panels to help align the panels which are put back
I think it is a good product, just need some experience on how to most effectively use the tool. Again I'm going to go back to the concept of the learner kit. Before investing in a big, expensive kit with all the bells & whistles, buy a smaller kit and experiment with a new product or technique. It may pay in the long run. I learned some stuff on the hull that I will use on the superstructure.