I’ve found that it doesn’t increase head turning because it’s not much wider than a single screen, but I can fit twice as much stuff.
Also I can read a much longer file of code at once, which is more useful than you’d expect..
The main downside is that since most people (obviously) use their displays in landscape mode, lots of websites and applications are pretty antagonistic to a tall and thin display. (Spreadsheets are often quite bad, but there are lots of places where people eat up horizontal space for padding or side bars that are suddenly super annoying).
There's a bit of a push to larger, ultrawide 5k2k monitors (e.g., Dell's U4021Q or the delayed-by-a-year-not-actually-available LG 40WP95C) but a pair of high resolution 27s is still a lot more pixel density. These bigger ones also tend to have lower brightness, presumably do to power and thermal targets per display.
That setup required even more fussing around with window setups. I also tried one monitor horizontally and one vertically, slightly better. But overall every two monitor setup has a problem in that my best viewing area (right in front of my face) is occupied by the seam between two monitors.
As for viewing more code, I also thought it would make sense, but I'm no longer sure. I ended up using my entire vertical monitor for a single buffer/file only, because splitting it vertically resulted in buffers that were too narrow, and splitting it horizontally defied the purpose of using a vertical monitor. I then realized that I'd rather work with a horizontally-oriented monitor and multiple columns, which provide me with more useful context from multiple files.
They are all on arms that somewhat encircle my position so it is no issue to code for extended periods on either of the "side" displays.