Lots of pixels have been published about the Neng Gao trail in Nantou. You can find articles here in English and here in Chinese. Most people ride from the entrance up to the Tian Chi cabin then bomb back down. I decided to hit the Chi Lai South Peak for a look. It is about 4.5 km of hiking/pushing and it takes a while to get up there.
This is part of what you are facing.
Once you get up there the oxygen is pretty thin. The peak is 3350, or so, meters above sea level. Apparently there is only 70% of the oxygen available there, compared to sea level. This site gives you a calculator to figure it out. Despite this, or perhaps because of this, the view from the peak is amazing. One of the side effects is that you can't get as much oxygen to your brain and you can't make decisions as clearly or ride technical single track as well.
The reward for all your pushing is this descent.
As seen below, the trail is much narrower than the main Neng Gao trail but it is a lot more challenging and fun.
Is it worth it the hour or two of pushing and carrying? Depends on your fitness and skill level. If you are fit enough, and technically skilled enough, it is.