Past Bethesda games have atrocious (read: broken) multi-monitor functionality. Even if most of it works there always tends to be some bits that just don't.
In Fallout 3, any terminals had unreadable text and the pipboy menu was the same way. Other minigames were offscreen.
In Skyrim, books were impossible to read through and the skill-point allocation screen was broken.
One of my favorite things about Elder Scrolls Online is that it works flawlessly with three-wide monitors and I give major props to Zenimax for making sure to properly support the multi-monitor segment of gamers.
Can we expect fallout 4 to actually work properly with multiple monitors?