We let our Brown-phobia subside long enough to give this a fair hearing.

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[5.43]

Crystal Leww: I’m a big fan of Chris Brown playing the role of Replaceable R&B Male Voice. I am a big fan of him getting replaced by another male actor in the music video. The beach vibe is a little light for the changing autumn weather, but Streeter just floats on this. 
[6]

Edward Okulicz: The production is like a quenching shower of rain on hot sand. The song, save when Streeter and Brown’s voices sigh and glide in to each other, is more a nap brought about by starting on the cocktails too early by the pool. What happens is nice, but not enough actually happens in four minutes.
[5]

Alfred Soto: Rue, wist, regret — the track won’t stop. Brown’s rank Miguel impersonation or Streeter’s Rihanna impersonation – take your pick. 
[3]

Patrick St. Michel: Sevyn Streeter sounds really good here, and the way her singing and Chris Brown’s hop back and forth is a surprisingly nice element of “It Won’t Stop.” At first. As if hell-bent on proving the title correct, this song just keeps going without developing into anything beyond a muted back and forth. Take a minute off of this and you’d have something a whole lot better.
[5]

Brad Shoup: As an experiment in recording a Drake song with a little range, it’s pretty good. (In her lower register she bears more than a little resemblance to Aaliyah, so I assume it’s only a matter of time before she receives a Drizzy summons.) We’ve got a little surf arpeggiation and lapping background percussion. And when Streeter and Brown’s vocals are stacked, they become serrated. It’s the only way they got my attention outside of the chorus.
[5]

Daniel Montesinos-Donaghy: Here we have an old-fashioned duet with enough modern innuendo to not feel alien from the rest of the R&B radio playlist — thanks, “rocking your body to sleep” coda for soundtracking someone’s future Christmas dance smooching — and enough Chris Brown for you to make your mind up already. Brown was already pretty gifted in the Forever era at this superclean type of consensual raunch, and he calmly schools Streeter on her own song. He takes the large swathes of sonic space into account, trailing behind them, keeping his voice from overexerting itself, making his presence felt when he’s not singing. Streeter can’t, and instead works an awkward vibe, her performance akin to a clumsy lunge towards romantic emotions. But this self-conscious overreaching has a charming side to it, sounding more shy than neutered. Like last week’s Janelle/Miguel duet “Primetime,” this is more cute than scintillating — and perhaps tame mistakes outdo rougher intentions.
[6]

Anthony Easton: This is the first great Chris Brown song I have heard, and it is mostly made great by his lack of ego. He lets Sevyn lead, and often his contribution is a moan or a sigh; the words mean less than his desire for her. It’s a start. 
[8]