I found some of the moves difficult to copy exactly as the camera shots are not always very helpful. Furthermore easy movements are described slowly, whereas the more complex movements are demonstrated faster - although I appreciate that there is a lot that needs to be packed in when a workout is only 10 minutes long. However if you do the whole lot the 50 minutes does go extremely quickly as it is quite fun.
I do some form of exercise every day, but as I am 2 or 3 stone overweight, I do not consider myself to be especially fit. This workout does not tax me. Towards the end of the 50 mins, I feel it slightly in my legs and knees (I wouldnt recommend it if you have dodgy knees), but my pulse is not overly raised and I am not out of breath.