I'm curious, has anyone used this? What was it like?

I'm thinking of maybe making a character who uses it, but only keeping their torso and arms crippled (the head can be annoying with the blurry vision and no one wants to be hobbling around like a chump. OWB prevents your head from getting crippled anyway and then all you'd have to do is use a doctor's bag on your legs from time to time). The benefits, especially if you're not too bothered about using VATS or scoped weapons, seem pretty huge (with the limbs outlined you're looking at a 30% boost compared to something like Thought You'd Died's rather measly 10%, also bearing in mind Thought You Died is a level 50 perk and Eye for Eye a level 20). Even then apparently steady can completely offset wavering aim down a scope or the VATS accuracy drops from crippled arms (and it's available from DM vending machines - bonus). Apparently crippled arms also lower melee damage - but I'd wager to say the extra +30% damage would more than offset that (the wiki is a bit vague on the details for the effects of crippled limbs).

Apparently having a crippled chest means your actions can be disrupted - has anyone noticed this being a huge problem? I'm just thinking +30% on something like Esther would cause a world of hurt.

I think it gets to the point with Perks that some are just suited to a specific role, in this case an extension of Nerd Rage, and are not meant to be useful for most characters. Heck, some Perks are downright useless, but are good to have around when you level up and have to pick a Perk when your trying to build a gimped character.

Now to your question, I have not used this specific Perk, but I can see where it would be an interesting combo with something like Nerd Rage and others that dramatically increase damage or defense when you health is low. Be good for building a "Cornered Dog" kind of character. One that is nice and meek usually but if enough people push him around, he goes all ballistic on people.