According to Nick Launay, one of the two producers, the recording of the album was unusual for being largely written and created in the studio at a time when record labels have cut back considerably on production budgets. The few songs the band did take along to the first sessions were later altered significantly. Launay described a typical session as follows:
"Brian [Chase] would play lots of different drumbeats and we'd record it, chop it up and then make a groove loop out of it. Nick [Zinner] would then just jam to it, and we'd come up with an interesting rhythm part. Karen [O] would listen to that and come up with a vocal melody and then suddenly everything would fall into place."
The album sessions took place over several months in 2008, during which time there were numerous breaks "to get inspired".
It's Blitz! received universal acclaim from music critics. At Metacritic, which assigns a normalized rating out of 100 to reviews from mainstream critics, the album received an average score of 82, based on 36 reviews.The Guardian's Caroline Sullivan commended the band's more dance-oriented sound, writing their "glittery new disco sound suits them very well. It's all cool, brittle catchiness, with a debt owed to Eat to the Beat-era Blondie". Emily Mackay of NME wrote that "It's Blitz!'s heartfelt love letter to the transcendent possibilities of the dancefloor is an unexpectedly emphatic reassertion of why Yeah Yeah Yeahs are one of the most exciting bands of this decade", while Spin's Charles Aaron said that it is "the alternative pop album of the decade—one that imbues The Killers' Hot Fuss and MGMT's Oracular Spectacular with a remarkable emotional depth and finesse". Later that year, Spin would place the album second on their best albums of 2009 list. Theon Weber of The Village Voice said that Karen O "isn't revealed to us through the record's lyrics, which are as gnomic as ever, but through attitudes, tones, put-on sneers, and audible grins."Mojo gave it a score of four stars out of five and wrote that the band has "managed to mix the human and the electronic, the emotional and the artsy, the fashion-forward and the oddly retro."
Blender also gave the album four stars out of five and hailed it as "the sound of a band reborn with new momentum, and on an album that requires dancing, the message is clear: It doesn't matter where you came from. Just keep moving."Clash commented that the trio had achieved growth without distancing themselves from what made their name: "The album proves that they can provide epic music with personal themes, that YYYs can expand without losing what made us fall for them in the first place".Jon Pareles of The New York Times wrote that the band "grapple with separation and need, using dance beats to suggest the compulsive pleasure seeking that tries to drown out loneliness", and he commended their musical direction, stating "The band is echoing the evolution of postpunk, from dogmatic austerity to technologically assisted".Uncut's April Long gave it a score of four stars out of five and praised its "spirit of experimentation", stating "What unifies them is a warm romanticism that runs throughout, edging out Karen’s blatant eroticism of yore – even though there are more come-downs than come-ons, every song seems to glow from within".