Bulgarian Bag??? What you think and have you ever use it ?

http://www.bjj-bg.com/video/video/87-bulgarian-bag-1

One of the best equipments for BJJ I've ever used, (no matter GI, or NoGI). This is a short video of a workshop with the inventor of Bulgarian bag few months ago.
Have you ever use it, what you think about these kind of exercises ???

We made one, but never use it.

Actually, the original one is giving you much more exercises. I really recommend to all of you, who are interested in adding something new for workout.