Sorry, IMO, Joss Stone's singing is so over the top it sounds (and is) contrived. For me, her harsh attempts at authentic female black blues ruins the tunes. I'd much prefer to hear the likes of Jennifer Batten. Listen to Dirty Mind and Rollin' and Tumblin on "You Had it Coming"; now there are some dripping wet hot and sexy vocals with real, honest emotion.
Let's see, Jeff Beck likes her singing. James Brown liked her singing and sang with her live. Lots of the greats have. This is the restrained Joss Stone on this album. Check out the vids of the songs on youtube - Jeff Beck at the 02. She opens up a little doing them live. Or even see the Idol gives back version of Spell.
I completely agree with your assesment of Stone. She can definately sing, but there's nothing original about her or her singing style whatsoever. She simply sounds like a white artist who wants to sound black rather than developing her own unique vocal style. And this makes Stone a very boring and predictable vocalist to me. Nothing fresh or exciting, basically just an artist saying to people, "Listen how much I can sound just like a black singer with soul!", and that's about it.