Love...
The music. Especially if you have one of the better sound cards. The music was incredibly beautiful.
The lore and the books, even though some of the lore got scrapped or ret-conned in later games.
No censorship. The game was made for advlts, though it had an option to make it more kid friendly.
The dungeon names never failed to amuse me. Names like 'The Screaming Castle', 'The Flying Guard', or 'The Djinn and Troll'. Well, they amuse me, anyway.
it could be very challenging, with little to no hand-holding or direction.
The King of Worms and the Dark Brotherhood were genuinely menacing figures.
Hate...
The donkey-loving rassa frackin' dungeons. Holy crap, who designed those things? Sheogorath? I was so GLAD they changed that in Morrowind.
The bugs. Enough said.
The Void. (though it can be useful)
'Halt! Halt! Halt!'