I was pleasantly pleased to find ESO automatically detects and supports the eyefinity resolutions. However, NPC conversations are kind of awkward.
For example:
http://postimg.org/image/sg1j0o4yp/full/
This isn't really a "support" case as it is a bug report but you can't report those with a screenshot in the middle of NPC dialog. There are other oddities with the eyefinity resolutions but I have submitted bug reports for the ones I've found.