Jimmy Daviswrote a review of POC Joint VPD 2.0 Knee Guard on April 15, 2018
Familiarity: I've put it through the wringer
I've ridden these pads for a whole season and for my intents and purposes (mainly enduro, but also DH and dirt bike) they have been amazing. As people seem to have noted, they do seem to run a bit small, but in my mind this is actually a good thing because they don't slide around at all. In fact part of me thinks maybe they don't run small and they are just meant to be tight. For a soft pad the level of protection is excellent. I've taken some hard falls and not even noticed my knees hitting despite bouncing on them.
As far as on trail use goes, they are definitely not breathable enough to leave on for longer climbs when its warm. I always throw them in a backpack, but I ride up for the down so that's good with me. If you want a pad for XC style rides this isn't for you, but it's not supposed to be either. For enduro races, bike park laps, or anything in between these are awesome and well worth it though.
They are also certified EN 1621-1, which is a set of standards for testing motorcycle protection... So I use them when riding my dirt bike sometimes. I have fallen riding the dirt bike through a boulder field and it pinned my lower leg to a rock and thanks to these pads and good boots all I got was a bruise. I wouldn't use these for racing or anything, but if you don't have other protection and they're laying around they'll do.