I just completed JM Kettlebell workout also this evening. OMG I loved it! My calorie exp said it burned 440 calories, and for my weight, that sounds about right.
I'm not so worried about how many calories are being burned for now. I'm just trying to make it through the workout, focusing on contracting my core and good form. I was warned that without good form, I could risk injury. And I definately noticed the workout in my stomach, butt, and shoulders. It was great.
After the workout, I felt immediately stronger, and strangely...much happier, and less worried about the day's low points. hmmmph.