I know what you mean, John. For example, I can't stand Sinatra. That's right--can't bear listening to him, and it's hard to say why. Tony Bennett, on the other hand, I could listen to all day. Ella? No. Sarah Vaughn? Yes. Who knows why.
But now for the Gardot fans: Larry's point about the control she has over her vibrato is exactly right; I'd also say something about the speed of it--it's very fast, which to my ear makes it especially attractive. As for the writing: I think it's impressive throughout, but the one I'm most struck by is the title song, "My One and Only Thrill." The combination of the chord changes and the melody line in the refrain is just astonishing. Starting from "When I'm with you . . . etc., you just can't predict the changes that follow, and it modulates from major to minor and back in ways that, to me at least, are as moving as anything I've heard in a long time.