The quests were
IIRC the quests didn't change the game world any more than those of Oblivion did. Nobody reacted differently to you… unless you count the NPCs who gave you hints about the next part of the main quest.
Which reminds me… I never turned down a main quest giver's request. What would have happened if…?

What I remember best: the Liches, and the panic my invisible, fireball-toting, wall-destroying sneaker felt when she heard their howl in the distance (similar to the Daggerfall vampires). Being able to bomb my way through dungeon walls was paramount for my virtual survival.