The only recent examples of RPGs with NPCs that followed day/night schedules that I know of are the Witcher and Witcher 2. It does provide a major benefit in making the gameworld seem more plausible when you have to wait till daylight to visit a vendor or go to an inn to find someone on their lunch break.
Oblivion, Skyrim, FO3/NV all did this: NPCs would sleep at night (or go about their more nefarious business), stores would close and so on. They'd often stop for lunch and would find something to eat if they didn't have anything handy. You'd often find NPCs wandering the roads as they'd go and visit friends in other towns certain days of the week or month and so on. I think they were reasonably well done. Rather basic when looking at just one NPC but overall it worked.
