Not being a Chopin aficionado, I never quite feel qualified to comment in great detail on any of his pieces. This, however, may be his piece with which I am the most familiar, and of which I am the most fond. I remember first hearing it as a child, before I began playing piano or even knew who Chopin was. That first impression was obviously favourable, as I waited by the radio to hear what the song was, and I wrote the information down on a little piece of paper on my desk. Unfortunately, little pieces of paper had a peculiar habit of getting lost in my childhood bedroom; it wasn't until a few years later that I heard this piece again on the radio, and knew immediately that it was the one I had been searching for. I never lost sight of it again.
Russian pianist Valentina Igoshina plays here, in a clip from the 1999 documentary "Valentina Igoshina Plays Chopin", other delightful excerpts of which can be seen elsewhere on this site.