I use the spray cleaners and they do help keep the scum down, or break it down in time if you have a great build up.
With that being said, we had some work done on our shower by a professional to fill holes from an old shower door. He said always squegee the water off, or use a small towel to wipe it down quickly after you shower...including the head last. It was a pain to get in that habit, but now we do it and it seems to help the most...but we do have soft water, so it doesnt build up so much. I think the acrylic will stay much cleaner than the fiberglass in general, so hopefully it wont be a big problem.