ESLs are amazing and can still be amazing in less than perfect settings. The biggest issue is to make sure the wall behind is not straight to the speaker. If the speaker is too close to the wall behind and firing straight from it, the result can be disappointingly un-even.
I now have the best room I ever heard ESLs in, and using just one as a mono speaker really does alleviate many problems in small spaces, while in the past I used a pair either side of a fireplace, which was not splendid, but still good. Then I used a pair and latterly aa single speaker in a smaller room. The improvement brought by optimising one speaker in a small space really brought things up in quality. Now with an almost large room, about 17 by 19 feet, I have the speaker firing not quite diagonally. Minimum of five feet behind the speaker to the wall and six feet behind me. Still quite close to the speaker from the listening position. Amazing naturalness results.
Because the ESL is so coherent, it really does not matter about sitting close to one, or even two or four! Though one is best.
ATB from George