Due to staying the next half a year in more or less one place, I was setting up my home office space. It involved getting a serious external display for my 2011 Macbook Air. I’ve settled down on Dell Ultrasharp U2713HM. Unfortunately, although its 2560×1440 resolution is officially supported by my laptop, I couldn’t get it to work properly - I only got a scaled-down 2048x1152.
In the end, it turned out that this resolution is only supported via the displayport cable. I wish they wrote it somewhere, so I did.