I like mine - it is expensive but I love the outdoor pool primarily.
Mine has a decent sized gym floor, but I think that is easily replicated at plenty of cheaper gyms.
Class wise, they have a lot more on than my local council gym, and more than the cheaper gyms locally. But I find the classes can be a bit random - i.e. they are all advertised as for all abilities but things like the yoga and stretch and mobility classes vary absolutely wildly depending on who runs them. Worth asking in depth about this if you do a tour if that would bother you.
Then there's racquets - the one near me has badminton as well as tennis (and squash) which is great - but again depends what you'd use and on the gym.
Then the primary benefit for me is the pool: full size 25m pool inside (nothing other than the council gym has this locally) and a 20m pool outside. Both open for the full range of opening times of the club rather than me having to squeeze it into whatever random time the council makes available (understandably they prioritise club swimming and children's lessons but still very frustrating as an adult with membership!
I also enjoy the spa: my nearest has "just" a jacuzzi, sauna and steam room but the one 15 miles away has a bigger spa area. Some spa areas are gated so you can only use them if you're a member of that specific club, others aren't. My membership is corporate so I can use all the different clubs (though still not all the spas).
That leads nicely on to the main disadvantages: the mystery pricing, price increases, the fact everyone in the club pays different rates, the fact that they have tiers both of membership and of clubs which aren't the same thing. It's fine once you've worked it out but it pisses me off on principle tbh.
You definitely have to commit to going at least a couple of times a week, preferably 3 for it to be worth the money.