Sotomayor is a liberal, but what would you expect? Liberal presidents nominate liberal judges; conservative presidents nominate conservative judges (though some nominees turn out to be less than what their sponsors had imagined). Get over it. If you want one of your own on the court, elect a president who will nominate them. Political leanings, or ideological disagreement, are a poor reason to oppose a nominee, but President Obama had no other reason to vote against Chief Justice John Roberts or Associate Justice Samuel Alito. Some Republicans opposed Associate Justice Ruth Bader Ginsburg on purely ideological grounds, and some will oppose Sotomayor on the same grounds.
Sotomayor will get some justifiable scrutiny over her ruling in the racial discrimination lawsuit brought by New Haven, Conn., firefighters. Her unsigned opinion failed to address the fundamental constitutional issues in the case. She ruled that New Haven could throw out the results of a carefully prepared, assiduously unbiased written test for promotion because minority applicants failed to earn promotion, but she offered no rationale or constitutional basis for her ruling. Racial preference was the only explanation for the city's action; is that constitutional? The case is now before the Supreme Court, which seems skeptical of the city's actions.
Sotomayor will also be questioned about some impolitic comments she has made. In one instance, she told a judicial conference at Duke University that appeals courts are "where policy is made." The interesting thing about the inflammatory but essentially truthful statement is that she was so inarticulate in stating it. Look at this video:
Sotomayor also said that a Latina woman could make a better judicial decision than a white male. The implication seems to be that the Constitution, far from being colorblind, means different things to different people, depending on their ethnicity and gender. That assertion is a recipe for dissolution of the union.
Despite these gaffes, Sotomayor will almost certainly be confirmed, unless an Anita Hill-type of skeleton falls out of the closet. One interesting omission I've seen in every news article and bio I've seen on Sotomayor: There's no mention of marriage. I assume she's never been married, given the omission, but the failure to say so, or to explain her personal life, seems to be a serious oversight.