We have use points twice at CS during cruises solely for Atlantis access. It works great. The property looks nice if a bit worn, but you are paying for Atlantis access. We did not go into the rooms.
I could not really get a straight answer on fees beforehand. I think perhaps they make it up as they go along. Once it was about $30 for two people and once about $43 for 2A and 2C. Still way cheaper than the cruiseline excursion price!