Hated how uninvolved the NPCs were in Oblivion - they all just acted like (and oft resembled) old, retired people. I believe Bethesda lampshaded this in one of the recent Gameinformer articles by claiming that actors in TES IV could only support a certain number of actions on their schedules. Even Morrowind's NPCs felt more outgoing to me. They mostly stood around, but everything from their idle animations to the way they'd say
"my time is precious, so make it quick", they felt very involved and frankly downright badass.
With various NPC trades and things such as mines and mills near the towns in Skyrim, I'm hoping we'll see an actual working class. Wouldn't it be interesting if NPCs had to earn money before they could spend it in shops?