This trail is one of the most enjoyable I have ever done. But not because of the actual riding, but because of the remoteness, the lack of other people and the sheer seriousness of the experience.
I rode the trail alone, in mid-December when it was around 14F at the start, warmed up a bit during the day, and as I got back to the car park was around 25F. It was cold.
The climb is long and tedious, and after a few hours is verging on "too steep to ride" and entailing slow pushes.
Once the trail improves to the state where no more cars are going to go, there is a delightful and remarkably remote ridge to the top of the Farlow Gap. The descent begins delightfully, but I found that very soon I could not ride, since the layer of leaves was so deep, and the boulders so large that I was falling off every few feet. The long descent was thus a bit of a nightmare of carrying a bike over large invisible rocks covered in slippery leaves.
At the bottom things improves - a bit - although there were a few distinctly scary bits where the trail had washed away over small (30-50 foot) drops and being alone is probably not the best way to tackle the trip.
The trail still goes on for a while until the junction with the easier and much more accessible routes is made - though there is still a fun carry across a fallen tree to get to the paved road.
In summary, great fun, distinctly "interesting" if you are on your own, haven't seen anyone else all day, and it's very cold.