I'll be honest: The last time something happened to my custom UI settings, I didn't bother to recover them. They're sitting safe and sound in a neat little folder right on my system -- no need to even plug in the backup drive -- but to be honest, it's just not that big a deal. Between a better computer and years of familiarity with the game, extreme efficiency isn't essential to what I'm playing right now. Granted, I'm not doing organized raiding right now, so I can relax on that front, and I often play intermediate-level characters who gain new skills and playstyles faster than I can lay out new key bindings for them.
I'll probably break down in another month or so and load up a few basic mods: an auctioneer mod, my favorite unit frames and hotbars, and maybe a tracker or two if I'm working on anything involving repetitive farming and travel. Other than that, I find it helpful to fly light as I hop between characters with drastically different approaches to the game.
I used to mod my UI heavily, though, and I know how addicting it can be. I would compare it to a painting you never finish adding to; my husband might imply it's more like a scab you can't stop picking. Where do you stand -- are you a dyed-in-the-wool modder? Do you enjoy adding a few utilitarian touches to your UI, or is redesigning the entire look and feel of your display more your style?