This could be common knowledge but I haven't seen mentioned the fact that the ESO UI supports mods. I was checking out esohead.com and noticed they have a UI site at esoui.com.
I have mixed feelings about this. There are a lot of positives about a stable UI that you don't need to think about and that just works all the time. Generally, though, I like being able to mod my UI. The main frustration with modding comes from keeping them up to date and the fact that so many of them break on patch day. Generally if your guild has plans to raid or do anything major and a patch drops that basically kills your plans until the authors update their mods to work with the patch.