I got an X-9 rear derailleur from Fullerton Bikes (great shop!!!) and put it on my Marauder this week. So far it shifting smooth and crisp after very minor adjustments. I was fine with the X-7 that it came with until it started getting stuck, and rather than try to get it warrantied I just replaced it with some thing better. So far I am happy with it, but will give it a more in depth review after it has seen some time in the dirt.