Her my experience with the piece maybe that help you for your decision.
I have used the Shox.xtr for wave (Baltic and North sea) since September 2010. It works and it reduces chops tremendously. That´s the main problem on the baltic sea, especially for light sailors. Now I can sail faster and get later overpowered. The buttom turns get more smooth as hard hits after jumps.
The downsides are the high price and the lack of a security line for the tendon joint. I have build my own one for critical conditions and I will replace the base afetr 100h, as NP recommands.
The metal tube in the side gets scratched during use, but since the wall is think it is mainly a optical issue.
Victor Fernandez used it on all rigs during the PWA in Klitmøller and he did crazy jumps.
In October I was told that a supplier in Germany was starting the production, because North was skeptical about the quality a Asian supplier could reach. That seems to be the main reason for the high price. I do not know how easy it is to get the piece now.
Btw, I have use the North Power XTs for several years and they are reliable and wel functional. But in case you have an older model, make sure you replace the plastik insert with the metal one to stop the robe sliding. And rinse it in fresh water regularly.
Greetings from Denmark