I haven't read enough of Sotomayor's opinions to have a confident sense of them, nor have I talked to enough of Sotomayor's detractors and supporters, to get a fully balanced picture of her strengths.
I should add that the thrust of the piece is that Sotomayor isn't that sharp. That may well be true, but how do you asses that without thoroughly reading her opinions, and talking to broad range of supporters and detractors? I know. You use anonymous quotes!
Sarcasm aside, minorities and women are particularly sensitive to being told they're stupid--as they should be. It doesn't mean that there aren't any stupid minorities and women. But if you're going to make that case, you really should cover your ass.