The Good: The Fox 831 gives first impressions much like that of an expensive car or a work of art. Every contour, every inch of the fork just screams "look at me I'm better than you." It is truly an engineering masterpiece and Fox shows no intention of hiding that. Although many products are capable of looking nice to hide performance flaws, this is not at all the case with the 831. The 831 features a light yet stiff chassis, providing it with a steady base without the extra grams. A 15mm thru axle anchors it to the wheels, and although this seems to be a bit lacking for a dj fork, it actually provides an incredible amount of stiffness. The axle is quick and easy to use and requires little or no attention in terms of mechanics. The 831 also has Fox's CTD damper allowing for three settings of suspension tunability. Although this seems not to make sense for a dj fork, it actually provides a great variation of setups for different scenarios a dirt jumper might encounter, weather it is natural lines in the woods, slopestyle contests, pumptracks, skateparks, or a stair set. It is easily tunable for the riders liking and provides what is without a doubt the most responsive suspension I have tried to date. On top of that the 831 weighs in at almost a pound lighter than a Rock Shox Argyle RCT, which saves the weight to make the bike much more movable and controllable.
The Bad: The price tag is a bit high for a dirt jump budget, and even then some will argue that the performance difference isnt there to be worth the extra money. Furthermore there are some apparent problems. Fox, likely to save weight and increase profit margin, equipped it with a CTD damper, and although I am a fan of this feature, many riders would rather it feature one of Fox's dampers more geared towards freeride, giving it more internal strength. This comes from many riders sharing experiences of blowouts with the fork. Fox recently moved to a 34mm body for the fork, and that change was for a reason. The fork likes to develop a bit of movement between the crown and the top of the stanchions. This creates a creaking sound that for any rider can be a bit troubling. The fork also is known to require more service than DJ forks from other brands.
Overall the 831 is for a rider who doesn't want to compromise. If you have any connections to shops, or dealers, or you yourself can service it, I would certainly recommend this fork. I still know several people who ride very hard and have not had theirs serviced and are yet to have any problems with it. Personally I think this fork is on a level of its own, and although it has its drawbacks, it is the best fork for a rider searching for the absolute best possible setup.