OK I haven't had one, but have ridden in one a bit. I assume you have too before you ordered one?
They are quite 'extreme' ie. somewhat akin to a NH saddle and you'll find you are extremely close to the horse. On the safety front that's probably a good thing as there is nothing to hold you in so to speak. If you don't already have a good lower leg position you'll develop one very quickly from necessity as there are no blocks to give you a helping hand.
Horses for courses really, they wouldn't suit a lot of people and I wouldn't want one if I was doing a lot of SJing, but they are extremely light and suited me XC (I like the minimalist approach when it comes to XC saddles anyway!).
I believe they are very similar to the barnsby Xtreem which is what I have. As Gamebird says, they are VERY minimalistic, but once you get used to it they are lovely, but dont worry if the first few times you jump in it you feel like you are going to fall off!!
My daughter loves them -- she has two! They do rely on good balance though. As said above - nothing much to hold you in the plate - but very lightweight.