 "What You Waiting For?" received positive reviews from critics. Nick Sylvester of Pitchfork Media gave the song a strong review, rating it four and a half stars, and labeled it "fucking great". The website went on to rank the song 16th on its list of the Top 50 Singles of 2004. RJ Smith of Blender noted the song's new wave influence by stating that it could start a revival of Missing Persons, and Amy Linden of The Village Voice compared the "giddy, yodeling vocals" to those of Lene Lovich's 1981 song "New Toy". Jason Damas from PopMatters was mixed on the song, calling the opening "awkward" and the refrain "ridiculously dumb", but arguing that the song "is so frivolous and stupid that it winds up being brilliant; it pretends to be nothing more than party bubblegum and achieves its artistic criteria beautifully." Slant Magazine's Sal Cinquemani agreed, stating that "it's this impishness that helps make 'What You Waiting For' one of the hottest 'arrival' songs of all time". Richard Smirke of Playlouder found the track's production "crisp" and "edgy", and Jennifer Nine of Yahoo! Music called the song "itchily irresistible". Jemma Volp-Fletcher, writing for Contactmusic.com, rated the song nine out of 10, commenting that it has "irresistible commercial pull and a melody to die for" and that the track "makes the most of her unmistakable vocal and reflects that off-the-wall Stefani personality perfectly." Natasha Tripney from musicOMH gave the song a negative review, stating that "it'll become one of those tracks that's irritatingly catchy — but on this initial listening, Ms Stefani's debut solo effort is just plain irritating."
