Unlimited Fitness Class Pass (Navigator)

My wife saw this on the Cruise Planner for our upcoming trip and was wondering if it was a good deal? I suppose like any unlimited pass, it depends on how much you use it, but I was wondering if anyone bought this and whether or not they thought it was worth it?

We're on Navigator this week (boarding on June 15th) and have 5 sea days, so we figured we'd try to do a class each day. At $69, I wasn't sure if that would be a better deal than paying as we go? Also, is this something we can just buy on board?

I'm interested as well. Are the classes and passes the same on all ships? I'll be on the Jewel this fall.