the "upside down" mtb derailers in question are actually low-normal, not high normal. Traditional rear derailers are "high normal", meaning that the derailer will sit in high gear(small cog) when there is no cable pulling it the other way. Conversely, the low-normal derailers, as Ken said, will go to a low gear if the cable snaps. This will help you climb in the case of failure, but they also have the benefit of shifting better under load than a conventional derailer. This makes them good for short-n-steeps off road, and arguably, this benefit would transfer to steep climbs with a fully-loaded touring rig. Shimano started making these when they switched to the mtb dual-control set ups, where the brake lever on the mtb also works as the shift lever. They felt that it was a good time to introduce the low-normal spring, as ppl will be relearning shift action anyway, and now they know that up on the left does the same thing as up on the right, and vice-versa.
As you may have gathered just from this thread, many ppl don't like low-normal, "rapid-rise" derailers. The dual-control mtb shifters never took off, either, which is why you can find them killer cheap on jensonusa. The low-normal derailers never sold well, which is the most probable reason why Fuji specc'd them on your bike. They probably bought a buttload of low-normal LXs for dirt-cheap, knowing that most ppl are just looking for "shimano LX" on the sales floor, without regard to the spring-style of the derailer.
Incidentally, I like the low-normal action, especially on climbs, and i put one on my trucker. So, yeah, it reverses the usual action on my barcons, but i got used to that quick.
Last edited by surreal; 03-12-09 at 12:41 PM.
Reason: goofed a fact