Now that I've been playing the night update for a while, I have some thoughts to share.
The day-night cycling is okay. It's a little difficult to see some champs at night, but still possible. I think being able to pick them out requires a degree of skill and experience that is worth cultivating, and is a positive addition to the game.
But I HATE the night prey.
First off, many take the place of a large prey (sizes being S-M-L-XL), which means they may remove a champ from the map. And there is no way they can offer up gems in replacement, as there are no night champs.
Secondly, they are basically worthless resource-wise. Besides offering no gems, most don't offer many coins. I usually kill all Large and XL prey so that it has to respawn, adding the possibility of spawning a champ. That can't happen with night prey, so they just aren't worth it. Besides they will all disappear in the day cycle anyway, so the respawn issue is moot. Granted, the cycle is: Large prey --> night prey --> large prey again, so night prey do create a natural respawning, adding a champ possibility. But that does not outweigh my greatest issue with the night prey.
And that is this: Night prey are too aggressive. Bats and owls swarm you whenever you get close, including encroaching on another prey's territory. If you are in a hurry, they block your path and you have to kill them--which takes time and gives nothing back--or avoid them. I have often attacked something big and suddenly found myself surrounded by bats. They don't do much damage, but restrict your movement as much as a mammoth would. Being mobile is key when taking on big stuff, and I have died more than once because an owl or bat got in my way.
I understand how night prey can add some "realism" to the game, but if the game was truly realistic, one wolf couldn't take down an elephant. I play for fun. And night prey is an annoyance that does not add any.
One final nit picky beef: night prey ruined Green Hills. Green Hills was the only map without flyers and it no longer is.