From what I can gather, she is pretty much a doctrinaire liberal. Since there was almost no chance that Obama would nominate someone who wasn't, it's hardly surprising. The best repository of criticism that I've been able to find about Sotomayor comes from Jeffrey Rosen's piece in The New Republic. The primary argument seems to be about judicial temperament.
The most consistent concern was that Sotomayor, although an able lawyer, was "not that smart and kind of a bully on the bench," as one former Second Circuit clerk for another judge put it. "She has an inflated opinion of herself, and is domineering during oral arguments, but her questions aren't penetrating and don't get to the heart of the issue."In other words, she is the anti-Clarence Thomas. Rosen further reports:
Her opinions, although competent, are viewed by former prosecutors as not especially clean or tight, and sometimes miss the forest for the trees. It's customary, for example, for Second Circuit judges to circulate their draft opinions to invite a robust exchange of views. Sotomayor, several former clerks complained, rankled her colleagues by sending long memos that didn't distinguish between substantive and trivial points, with petty editing suggestions--fixing typos and the like--rather than focusing on the core analytical issues.This is the key point. Sotomayor, if confirmed, is likely to be a suitable (for liberals) replacement for Souter. She is also unlikely to change the group dynamics of the current Court, nor would she move the needle in any real way.
My view is that group dynamics are especially important for this Court. The four conservative justices -- Scalia, Thomas, Roberts and Alito -- are pretty much of the same mind. The liberals -- Ginsburg, Breyer, Stevens and Souter -- are also pretty much of the same mind. The swing vote is inevitably Anthony Kennedy. Kennedy's style of judging is (to be charitable) a bit idiosyncratic and my sense is that he's often less likely to look at the law than at the tone of the argument that's been made. My fear was that if Obama had picked a liberal with strong persuasive skills that might make it easier to influence Kennedy, and by doing so he could have changed the balance of the Court with this pick. I don't see Sotomayor doing that, especially if she is as personally abrasive as it appears.
President Obama is going to get two more picks soon -- Justice Ginsburg is quite ill and Justice Stevens is quite old. The next pick could be a game-changer. Here's the name to watch: Cass Sunstein.