I spent time sitting in the coop today, watching the chickens while they ate. I tossed some corn into the deep litter to give them some fun in looking for it and that also gets the litter moved around a little at the surface.
The litter was nice and dry on the surface and slightly moist in the layers underneath, just as it should be. I noted that the kitchen scraps I had been throwing in the litter are nowhere to be seen now, even the onions and potato peelings that the chickens won't eat.
Manure disappears just as rapidly, as I can turn it under in the area under the roosts on one day and a couple of days later do it again and find no evidence of the manure turned under just two days previously. There is no smell in this coop and I can pick up the litter right under the roosts and place it up to my face, take a deep whiff and only smell composted leaf material. Smells like the forest.
I'm very happy with the way the DL is working this winter and it seems to have just the right amount of moisture retention while staying dry at the surface, where the chickens walk. The level of ventilation in the coop seems to be working well also and has been easy to adjust after rainy spells in order to stabilize the moisture in the DL.
No frostbite on combs or wattles, though the temps are -6C to -18C here and the coop has large open areas at the front of the coop. The DL seems to keep it warmer there and the ventilation keeps moisture from collecting at roost levels at night, so the chickens are staying warm and well.
Edited to add: Just noticed the controversy on the forum about scraps and the laws about them in the EU, so wanted folks to note I'm from the US and we have no such laws in place. I hope we never do, as kitchen scraps for chickens is as old as time here for backyard flocks and is a supplement to their diet, especially in the winter months.
Sorry if this post rouses any ire about the scraps but we are free to do that here, so not promoting anything illegal at all. Different strokes for different folks, as they say.