Yes I have (and so have a significant number of others) and yes it is.
It is, in my opinion, very good practice for kitesurfing. There are major differences but the more you get sorted out before you venture onto the water the better.
As a pre-cursor buggying is much easier because of the inherent stability. Smaller kites can be used and once again you will learn basic skills of how to use the wind, and what angles of travel work.
That is not to say you couldn't jump straight to mountainboarding, or even kite surfing. It is just that as a progression I believe buggying is simplest to learn, mountain boarding next and lastly kite surfing. The most important thing with all of these activities is good ... almost instinctive ... kite control when using monster kites.
Of course if you are a good surfer you will understand the board skills. This means that you will only need to learn the kite control.
Further details on application
Rgds ian
