I am really into anything cardio dance related, I do 2 Zumba classes per week and 1 Cardio Hip Hop class at the gym I go to nowadays.
Usually instructors will do the same routines for awhile and only add in new ones here and there, so that if you go often enough you get accustomed to it and I find once you are at least vaguely familiar with what the instructor will do you can get a good workout. It's good not to get TOO comfortable, the novelty is important, but I always find when something is brand new to me I never get as good of a workout because I have to stop sometimes to watch what's going on or do the move wrong or whatever.
And the universe of possible cardio dance moves isn't infinite. You'll find that there's the same basic steps with variations used often times!
I lost ~30 lbs on cardio + weight lifting + watching what I eat (over a year period though, because I gained back some and lost some again). I have been on a Zumba/Cardio Hip Hop + watching what I eat regime for 2 weeks and did lose 4 lbs in that time. But I had been retaining water from TOM so that's not a normal jump. I'll keep reporting back whether the Zumba/Cardio Hip Hop + sort of diet is working. I've gotten busy with working and am scared of the soreness of going back to weight lifting, so that's postponed for now.