One of my favorite parts about ElvUI is that it comes with an in-game setup process that'll help tailor the UI to suit your needs. But even if you decide to stick with manually updating it, what ElvUI brings to the table makes the sacrifice more than worth it. Historically, you've always had to install and update ElvUI manually, and while this isn't too much of a chore, there are a number of newer addon managers popping up that allow you to update it along with your other addons. The tradeoff, of course, is that you're also getting rid of the fantasy-themed UI altogether. ElvUI replaces every single user interface element with a sleek redesign that is a lot more modern and readable.
This is one of the most popular total conversion addons for World of Warcraft.
(Image credit: Blizzard, modded by Tukui)