I can't speak to the Powersupport, but I do use a Brando antiglare which costs a third less, and it works perfectly: easy to install, very fingerprint resistant and extremely durable.
With installing any kind of screen protector on a screen as big as an iPad, you need to have (i) a clean environment, (ii) clean hands (wash and dry your hands thoroughly) and (iii) setting aside the time 15-30 mins to complete the task (and making sure people around you also leave you alone). Alternatively, if you can get an extra pair of hands, it helps enormously when you are trying to position the filter over the screen.
I suspect that some of the botched installation jobs resulted from impatience and inexperience, rather than poor or defective quality of the filter itself. If you've never done it before, it can be a difficult task. (It helps to watch some of the how-to-do-it videos on YouTube first.)