Adding to earlier posts, be aware that your idea of fun and difficulty is not all ways the same as the modders.
OOO is a good example its a beautifuly made and fantastic overhaul but many areas of it go from adding to the danger / excitment, to making it unbelievably pwning, but not all of it though don't worry about that.

If your idea of oblivion is of your godzilla build, taking on an army with elite melee, magic, marksman skills, whom procede to use multipule summons of just as hard backup foes.. then you will want this type mod.
However if the thought of insta dying many, many, many times from among others self healing, regenerating, bosses with absorb, reflect, and resistance effects, or just unlocking a chest, unless playing with powerful specific builds and skills then avoid overhauls.

So my point is save yourself some time, ask around, read the faqs and read mes, unless you're sure vanilla oblivion is not enough for you no matter the type of mod you want.

Haha I've experienced that second part a ton. Love having 10 minute battles with people who run around casting spells and healing themselves but won't necessarily kill you or die. I usually end up putting the difficulty slider down since i realize that I'm better than they are and I don't want to waste tons of times and potions and welkynd stones trying to kill a coward.

Yes it can require power gaming a bit, and their cowardess is a real annoyance, if you combine the wrong rpg build, try 50% weak to frost, shock, 20% magic weakness..
Being only good at sneak and h2h, no magic, no self made potions apart from fatigue, lowish level and having their multipule per caster level 15 odd summons insta spot you..
Reloading three odd times, only then dying to a chest??? thats my reason for warning people, about sticking to vanilla oblivion..
Unless positive about wanting the change, overhauls are not designed for the role in rpg.

Lol I just installed an attribute mod so I don't have to worry about attribute bonuses and can still roleplay fine. Makes it way easier and funner, and getting +5 is a pain in the ass anyways.

I generally play with mods, as I was getting quite bored with the vanilla game. However, do to recent events I only have Oblivion on my PS3 for now, and I'm actually having a lot of fun. (9 hours in just over two days.) I sometimes prefer the "simpler" game over the heavily modded counterpart.