Mud, Mud, and more Mud!
Montezuma falls by itself is well worth a visit, and is made even more fun by MTB access from either end of walk.
The upper section (above the falls) is closed to vehicles and is a beautiful ride under the myrtle forest, across a stream, and past some old mining tunnels. This section is quite flat, and should not challenge most riders (as long as you're happy to get wet!)
The section below the falls, where 4WD access is allowed, is very muddy, especially during the winter season. There are a couple of creek crossing with steep pinches, but for the most part this is also a pretty easy ride, following the old tramway. Watch our for 4WDs (although you'll probably be faster than them in some of the trickier sections).
Overall this is a very beautiful track; the falls are definitely a highlight. Not very difficult, but you'll be riding through lovely rainforest and myrtles for the most part.