[5] Cars keyboardist Greg Hawkes recalled the first time he heard the song in an interview, saying, "I remember hearing 'Just What I Needed,' thinking ... 'Wow, that's pretty cool.

"[6] The song first appeared in 1977 on Boston radio stations WCOZ and WBCN from the demo tape, along with its future follow-up single "My Best Friend's Girl".

[3] DJ Maxanne Sartori, who was given the tapes of these songs by Ocasek, recalled, "I began playing the demos of 'Just What I Needed' and 'My Best Friend's Girl' in March during my weekday slot, from 2 to 6 p.m. Calls poured in with positive comments.

"[15] In 2003, pop rock band Fountains of Wayne would in turn copy the Cars' take on the riff for their song "Stacy's Mom".

[22] "Just What I Needed" has since been covered by several artists, including by the Strokes with Jarvis Cocker in 2011,[23] the Killers in 2018,[24] and the Red Hot Chili Peppers in 2019.

[25] AllMusic reviewer Donald A. Guarisco praised it as "a clever pop song", commenting that "Elliot Easton's fiery guitar leads duel with Greg Hawkes' icy synth lines over a throbbing pop/rock backbeat while Benjamin Orr lays down a fey, detached vocal that captures the sarcastic edge of the lyrics with skill.

"[26] Billboard said that it was energized by a "driving, propulsive beat" and enhanced by "feisty rock guitar lines" and "a winning harmonic vocal style.

[23] Classic Rock History critic Brian Kachejian rated it as the Cars' 2nd greatest song, describing it as "a combination of Benjamin Orr’s original-sounding voice, Greg Hawkes’ fascinating keyboards, Elliot Easton’s sparkling guitar, and that rock meets dance meets punk groove set up so perfectly in the rhythm section of Benjamin Orr and David Robinson.

"[36] Weezer frontman Rivers Cuomo singled out the song as the reason for selecting Ocasek to be the band's producer for their debut album, recalling, "One day I was in the grocery store and I heard 'Just What I Needed'.