I think a lot of people don't like having their characters maimed for the same reason that they don't like having their characters tortured or sexually abused - it's profoundly deprotagonizing. Nothing says "you are not the hero of this story" like your arm falling off. That said, "you are not the hero of this story" (or, perhaps "this is a story that doesn't have any heroes") seems to be a theme of LotFP, so...
I still think it's important to get your players' consent before maiming their characters. Make sure you understand their limits and their interests. Maybe get each player to give you a list of the most terrible things that they would be okay with happening to their character, and underline the things that are terrible but also particularly interesting or "in style" for their character (ie. "right now my character is handsome, but I think he would be awesome with some terrible scarring" or "eyepatches are neat" or whatever).
I'd also say that it's a good idea to give players the option: your dude doesn't have to die of dying, but he'll have some consistent problems. Or, alternately, you can give up the character and move on.
I'd also say that it would be most fun to use maiming as the beginning of a plot, rather than the end. Assuming it's stylistically appropriate, consider letting your character go off in search of some kind of prosthesis, or super-intense healing magic, with all the risks and terrible bargains such things entail. I mean, what's more awesome? My character doesn't have a hand anymore and that's it, or my character lost his hand, grappled with it for a while, then beat up a demon and stole his hand, which continues to give me problems and plot hooks forever?