Oh, I still play almost entirely vanilla. Have yet to get bored enough to do any really major modifications.
Ah...well, I put over 500 hrs into the 360 version (I'm quite positive Oblivion and Dead Rising are what red-ringed my first 360) and as soon as I learned about PC modding (I'm real late to the scene) and what it could do, I bought the PC version, and installed FCOM, RBP, LAME, Deadly Reflex, and Midas Magic. Have not regretted it...but then, i put so much time into what I call "super vanilla Oblivion" (without any of even the Unofficial Patches...) [that is to say, SVO = Console Oblivion, heh]. Deadly Reflex's "Stab 'em while they sleep" feature is incredibly brutal, and at times can really make you think "holy...do I REALLY wanna kill this guy/girl?"
Gates... Those damn Oblivion gates. Every time i need to go inside, close damn thing...
The only thing that could make me have to go inside those damn things was quests. I would refuse to go into the ones I didn't have to...that is, until Midas Magic came along. Now it's actually worthwhile to go into the damn things, as the reward can be quite great.
Hmmm...something that annoys me about Oblivion...ah, I know:
NonVanilla Annoyances: Mods that haven't been updated in years, and yet have so much unfulfilled promise.
'nilla Oblivion: Extreme levels of fugly on the characters. my friends and I still have nightmares about "You're the one from my dreams" being coupled with the up-close-and-personal zoom of the camera.