What is the best Interface for World of Warcraft

The default interface is pretty good. Alot of people don't use any sort of addon, even when raiding. It all boils down to personal preference. Some people replace all the default action bars with smaller ones, and have nearly every skill macro'd to key and mouse binds and that is the only change they make. Some take a minimalist approach and have hardly anything onscreen. Still others heavily modify their screen and have meters all over the place barely having and room to see what they are doing. It also depends on the speed and power of your computer. If you have a lower end system, you will not want that many addons running at the same time, whereas if you have a more powerfull computer and bigger monitor, you can heavily modify the interface.