Upon its release the album received positive reception from critics and was a commercial success. The album was included on NME's album of the year list for 2003, and Rock Sound's 101 Modern Classics list. debuted at number 12 on the UK charts and achieved Gold certifications after a sales of 100,000 a year after its release on 29 October 2004.
The album features brand-new versions of the songs from their previous extended plays. Tracks like "Red is the New Black", "Juno" (renamed "Juneau"), "She Drove Me To Daytime Television" and "Escape Artists Never Die" were all re-recorded from preceding EP's Four Ways To Scream Your Name and Between Order and Model. Previously, the track "Waking Up" was tentatively titled "Summer's Dead and Buried".
In 2012 the band released a live album titled Casually Dressed and Deep in Conversation: Live and in Full at Shepherds Bush Empire. The live album was recorded at the Shepherds Bush Empire in London in July 2010. The live performance's setlist featured the debut album in its entirety, plus additional tracks from other albums in its encore. The album was announced in January 2011, with no tentative release date announced but a teaser trailer was posted. The live recording featured guitarist Darran Smith before he left the band in late 2010. He was replaced by Richard Boucher, whom was a member of hardcore punk band Hondo Maclean. The album was released in early April 2012 and was made available through the band's online store to purchase.
The album received very positive reviews from the British music press upon its release. With NME writer Dan Martin gave the album at 8 out of 10 and praised the album quite considerably calling it a "fearsome debut" and stating that: "It would be unfair on everyone else to call 'Casually Dressed and Deep in Conversation' the first great album to come out of all this. But what is true is that this fiery, dynamic hulk of a record will be the first to break properly out into daylight." It was also featured at number 17 in New Musical Express's albums of the year list for 2003.
In 2012, British publication Rock Sound added Casually Dressed & Deep in Conversation into their "101 Modern Classics", placed at number 33. They considered the album more of a classic than Sum 41's All Killer No Filler and Botch's We Are the Romans. Stating that "‘Casually Dressed…’ evidences a remarkable young band who, on their debut full-length release, were already the finished article, establishing a sound that continues to define an entire generation."
^ ab"Rock Sound’s 101 Modern Classics: 49 - 25". Rock Sound. Freeway Press. 4 July 2012. Retrieved 30 July 2012. "The album that dogged the Welsh wonders for the best part of a decade before they finally made their peace with its infinite charms, ‘Casually Dressed…’ evidences a remarkable young band who, on their debut full-length release, were already the finished article, establishing a sound that continues to define an entire generation."