Fast travel = You can't unlock another location
2. Sleep = +EXP (except werewolf)
3. Social = At the begining of the game, you already socializing
4. Day time = Shop open, people are lot outside the house, people do their work
Night Time = People sleep, easy to do a sneaking skill
The first time i played skyrim, i never care about the time of the game, just like you "Who cares it was sunny when i killed the dragon"
but.. the more you do the quest (especially killing people quest)
you will love the night time of skyrim