Glad you go the chance to play with it.
I honestly replaced most of the gyms with spas as they pretty much function just like one except for fancy pancy stuff in it. I saw sims using the treadmill and even the climbing wall on the spa lots as well. Watching the fizzy drink tray get filled and sims grabbing a drink now and again. I really do love the items in it and having my sims go out to just get a foot massage or just spend money on a yoga class.
Course I had sent my sim I been playing with in Ecoliving ot take a shower there because her way of living is rough. XD Couldn't afford massages though.