Recent understanding of life evolving has very little to do with the environment, regardless of environment, life can evolve, even in environments that would be considered problematic for life as we know it. While the environment has a VERY direct effect on the resulting lifeforms, the environment is almost irrelevant to whether life exists or not.
The problem with Uranus as a life-producing planet is that just as soon as someone would become acclimated to a given environment, it would change instantly to the exact environment you don't want. After 20 years of darkness, all of a sudden, everything is lit up like a christmas tree. Big problems for anything evolved to deal with darkness. The reverse is just as problematic. Honestly, I can't see how anything could evolve to adapt to an environment that changes so drastically, unless they migrated away from or towards the light as the situation changed(ie as the planet moved around the sun, the creatures moved to their best environment, light to light side, dark to dark side, etc)
That said, lightless, cold environments, such as the dark side of uranus, would probably be populated with creatures similar to what we find at the bottom of our oceans. Very specialized, very alien creatures that are uniquely adapted to such a life. Big eyes, or no eyes at all would be standard. Creatures using sonar(ala bats, etc), or other forms of non-visual prey detection (hearing, touch, etc) would be standard. Most grazers would probably be on the go all the time, and many predators are likely to be "trap-style" predators, waiting for prey to enter their kill zone. The most successful predators are likely to be highly mobile trappers, ones who, if they fail at the trap, are capable of pursuing prey some distance.
In fully lighted environments, the normal sleep cycle of night and day would be supplanted by probably near 100% consciousness, with rest taken as appropriate within those hours. A "sleep time" would be almost unheard of. Predators and prey are highly likely to be reflective of standard predators and prey of our world, with the noted exception that NONE are likely to have developed night vision of any kind, and they are also highly unlikely to have developed any senses substantially beyond sight(for predation), but prey are likely to have highly attuned senses of hearing and smell as well.
If I were to use a world like this for real gaming, I would make some way to have the planet ALWAYS facing in one direction, without worrying about the light and dark sides flipping sides. Perhaps the gravitation and rotation always keep one side facing the sun, or something.
Of course, then you have a near instant campaign. The light side and the dark side leave each other alone, each with societies on their appropriate sides. The two sides rarely interact. Until the planet suddenly shifts by 90 degrees or something. Half of the dark and half of the light societies are now on each side, big problems for the appropriately misplaced society. What happens? Does one side help the other, does one side annihilate the other, who knows. But if you put the PC's on the edge, between darkness and light, at the start of the campaign, and plunge them into either darkness or light between the two sides, you can be d**n sure you're going to find out.