The music is taken at a slow, dirge-like tempo; towards the conclusion Costello offers a brief guitar solo that repeats two dissonant notes.

"[3] Attractions bassist Bruce Thomas later expressed his dislike for the song, commenting, "Elvis was trying really hard to do the psychopath in 'I Want You' and all that.

[10] Jeremy Allen of The Guardian named the song one of Costello's top 10 best, saying, "The lyrics and music together are intimately intense, like someone breathing down your own neck, making you shudder, but the melody is irresistible too.

[10] Gavin Edwards of Rolling Stone said of the performance, "[Apple] metabolizes every molecule of the song’s poisoned atmosphere.

"[10] Costello also collaborated with hip hop band the Roots to perform a version of "I Want You" in 2013; Questlove said that the song "is pretty much the soundtrack to every relationship I've ever had".

[2][11][12] In 2010, Steven Page released a cover of the song recorded with the Art of Time Ensemble for his second solo album, A Singer Must Die.