I am totally anal about this, but after much thought, decided to skip the sp for the new iPad. I had protectors front and back on the orig iPad and the iPad2. But I also use a Smart Cover and keep the unit in a small attache case designed for tablets, so I decided the sp would be overkill.
I've always bought good quality ones, and never had problems with degrading the screen quality, but in doing side by side comparisons in the past, without the sp was a bit better. With this new display, decided I did not want to compromise the quality unless there was a compelling need to do so.
What I expect to do from time to time is use a non-alcohol based cleaner, same used on glasses, and a microfiber cloth. Also decided I will probably keep this iPad for 2 years - LTE was the big thing for me - can't imagine what they can add next year except for a better camera, so with that, will get the AppleCare+ so if anything real bad happens to the screen, even a few scratches, I can replace the unit up to two times.