The majority said that the fear of litigation by black firefighters who didn't do well on this test didn't justify tossing the test. So I guess the lesson here is that when you are going to test for promotions you had better make sure the test is race neutral.
The four dissenters found that the white firefighters had no right to be promoted anyway and had not seen black candidates promoted over them-- only the test was tossed out. This, the dissent claimed, did not warrant the court's interference in New Haven's attempt to solve what it considered a legitimate problem with the tests.
It's an embarrassment for Sotomayor, for sure, she's just been reversed on appeal and no judge ever wants that to happen. But it's important to note that four justices on the court agree with her, in whole or in part, so it's not as if her lower court ruling was outside the mainstream or completely implausible.
Sotomayor's detractors will claim that this ruling is proof that she's outside of the mainstream when it comes to affirmative action cases; her supporters will counter that the case was narrowly decided 5-4 and that all lower federal appeals court judges get reversed from time to time.
Certainly it will be a topic at her confirmation hearing next month but it could have been a lot worse for Sotomayor. Had the Court unanimously rejected her rationale in the case her detractors could have seen it as proof she was not ready for prime time but her analysis only lost out by a single vote and along ideological lines.