Is for instructors with no personality or ability to put their own spin on classes, come up with own ideas and give customers what they want. It's the McDonalds version of exercise. Great consistency if you're lazy or want to know exactly what you're getting but rather bland and impersonal. Costs instructors an absolute fortune too so I won't ever go that route myself.
If you can find some good non zumba classes near you I'd go for them but maybe try a few and pick what you like best. I only have experience of classes around Hastings, Bexhill, Rye, Battle etc. but where we have good instructors, zumba has had a poor reception generally and only makes up a tiny percentage of classes offered currently. Hear that this is different in London and Essex though where people want to do the 'latest' thing (it's hardly new) just for the name.
Probably fair to say we have an older clientèle but the younger customers seem to agree too with above and I'm a 27 year old instructor if that matters. One centre I'd say the instructors are the worst, happens to be the one zumba has started to establish itself in as well (and yes I occasionally cover non zumba classes there so may be biased).
They run them at my College for ladies who want to wobble their way around my gym, sweating and not clearing it up after themselves because they close their eyes and imagine that Patrick Swayze (pre-dodgy-cancer-look) is dancing with them.
Boxercise is better.
My Self Defence classes are best!