Bought a pair of speakers once that sounded great on demo, at least with what they were demoed with. Stupid me. If I had seen the measurements first, I would never have bought them. Got them home and no position, no toe-in, nothing would make them sound right with a wide range of music. Sometimes brilliant, sometimes just something wrong. Found out later that there was significant frequency response/directivity issues.
Learned my lesson. I never bought speakers again without having measurements even if that limited what I could buy. There are just too many things that can be done wrong in a speaker, driver resonance, port resonance, cabinet resonance, frequency response, distortion, distortion over volume, directivity issues, thermal compression, less than ideal cross-over design, etc. When listening to new speakers, there are so so many variables, that is hard enough to say "I like these", let alone pick up on the design flaws that may only become self evident with some music, and then being new speakers you think is is me, is it the room, is it the amp?
Speakers are one area where measurements are really critical. It is not going to tell you if you like it or not for the long time, but it can very much highlight flaws you may not encounter in early listening that you will eventually not be able to live with. At a more fundamental level, directivity plots will help you know how it will work out in your room, the range of toe-in you can use, even whether compared to your existing speakers they may be darker or brighter. Let's not forgot amplifier interaction as well.
When you write it down, you realize that buying speakers without any measurement is a really risky proposition.