Okay, so maybe this should have been obvious from the description, but the Idiot Savant Perk in Luck does work on ANY XP gained if it triggers at the right time, including finding locations and quest XP.

I just have one Rank in the Perk, but I just got the "giggle" after completing a quest and gained THREE levels at one time.

Idiot Savant may be the single best way to quickly level up in the game. Nothing competes with hundreds or thousands of XP at once. With all 3 Ranks in the Perks, and a low intelligence, most every quest you turn in will have a good chance of leveling you up, sometimes multiple times.

This has been known since day one, you quick save before turning in a quest and load it until idiot savant activates.

Well, I just discovered it after 140 hours of playing. My "idiot" character is leveling faster than my other two characters combined. I kind of like the fact the perk makes her appear a little unhinged. I mean, she'll set raiders on fire with a molotov and then giggle about it.

I'm also doing a "pure" VATS build, based on Agility and Luck, and it is pure gold. Better Criticals, Critical Banker, Grim Reaper's Sprint, Four Leaf Clover, and Action Boy/Girl is NUTS. Can't wait to add Gun Fu into the mix.

I had a high agility high perception character, it was so OP it broke the game, you'd have more VATS moves than the game UI could account for, and they'd all have a 95% chance of hitting too

Then its not luck anymore

How often does it activate with a "normal" inteligence level?
I like to have science for making mods, anf for that you need a good Int.

Then don't take Idiot Savant, as that's just a waste of a perk that could be spent on something far more useful, especially on INT builds where you need every perk you can get.

I figured I would get a more informed answer from a random internet search, so I did one.

It seems that after an Int of 4 you are half as likely for the IS perk to activate.

However, if you "work the system" (save & reload before turning in quests) then it will return a very high percentage of Xp for the only two perk points to reach the second rank of the perk.
So, if you are "that" kind of player it is fully worth it.

I still think I will just stick with my 10 Int characters for now...I like being a "know-it-all" ingame, since I cannot be one in real-life. (lol)

..I did both, unfortunately.. getting Idiot Savant as a rather late perk choice for my high Int character. I was rather stunned the first time the sound effect keyed. It is so far over the top. I almost wish I hadn't taken it at all.

I knew about the sound effect. I agree, it doesn't fit a High Intelligence character - but if you do what I did, make a character based on low Intelligence (only 3 for Gun Nut) and Luck, who loves to screw around and is a bit of loon, it's great. It is honestly pretty hilarious to turn in a quest and cackle in an NPC's face, or start laughing in the middle of shooting raider's in the head. The Perk picture should be your clue - it's for a nutty "special" character.

Yeah, im noticing the more perks I select and as I progress them, they are actually doing cool things that you don't expect. The short descriptions of what stuff does in the game makes them seem like they do little or nothing at all, perks and modding. It is kind of like the perks you got automaticly in Oblivion when you reached the next tier.

I have an 11 int character and idiot savant still works. It's not often but during my playtime today it happend on two named enemies. Both were over 400xp kills.