I think SR's English is pretty awesome. Not awesome because it sounds so natural and native (it doesn't, although it's remarkably good for a non-native), but awesome because she makes it her own unique musical tool. She has quite an "accent," but it's certainly not a FOtB Japanglish accent... it's something else entirely, whether it's an affected thing or just colored by her own lens. Her deviances from standard English are part Japanese accent, part her own thing. Her mispronunciations are delivered with staggering confidence. It makes it a blast to listen to. I think in that regard categorizing her with Björk is perfectly acceptable.
Oh and let me mention that as a songwriter I am totally jealous of SR's ability to write hooky lyrics in her
second language.
So I voted yes. Also, if there were a "Should SR sing in <any language>?" poll, I would vote yes.