This is ABBA's best song. The syncopated drum-track in the verse is smart and the general feel of the song is cool. But the best part is the harmonised singing in the chorus. The background harmony which drops down a tone or two (imagine Jonny Marr shifting his guitar down two bars in a chord progression and you're there) is total class.
Such a ludicrously sentimental depiction of one party's feelings after a relationship breakup that I can imagine few would admit to liking it. However, it's a beautifully-crafted and wonderfully performed song with a superbly effective arrangement. I admit to liking it despite its total sentimentality and lack of any kind of coolness.
One of several great tracks from the end of their career as a band. Fantastic recording quality, too. Originally the B side for "One of Us", omitted from "The Visitors" but included as a bonus track from 1997 onwards.