I've been using 2 x 27" 1440x2560 (Dell U2715H) for 2 years now. (Dell monitors are typically a pretty safe purchase in this respect as all the mid range ones seem to come with rotating stand.) I've been very happy with this setup, and I've no intention of changing. It's a good aspect ratio for editing text and viewing PDFs and whatnot, and makes very efficient use of desk space. My 2 portrait monitors are only about 12 cm wider than one landscape one.

I also don't understand why more people don't use it - but perhaps people try it out with a 1080p monitor, find it a bit cramped, and decide against it. (I used 1200x1920 monitors for a while, and the screens always felt a bit too narrow even with that. A lot of programs and sites seem to assume you've got a monitor that's at least 1280 pixels wide, so you end up with extra scroll bars, cramped UI, or stuff that's simply inaccessible.)