I go 4 times a week. My instructor is AMAZING. She mixes hip-hop, latin, african, belly-dancing and more. I went to one other who only did latin and hated it. There are about 150 people at mine. It's $5 per session or a card with 10 sessions for $35.  One girl has lost 80lbs since September, and another 40lbs since September. I'm on week 4, and I haven't done much with my diet, so my weight hasn't changed, but everything is becoming more tight and tone. I'm adding Atkins to the mix this weekend, so I will hopefully drop weight quick.
DO IT. You will not regret it. Main thing is to find a good pair of shoes with very little tread. Otherwise you will really hurt your knees.