The Catholic Church's tenets and values are hardly a mystery. If one is a practicing, faithful Catholic then it's safe to conclude that one's principles are mostly, if not entirely, consistent with those proclaimed by the Roman Catholic Church. Even if one is a nominal Catholic or a lapsed Catholic, then barring contrary information, it's safe to assume that one's upbringing was shaped by those same principles.
But as a matter of practical course, it doesn't seem to have much bearing at all anymore. The modern Catholic Church is (a) pro-life on both abortion and execution; (b) pro-life on war - i.e., anti-war; (c) traditionalist with regard to family and sexuality; (d) quasi-monarchist with regard to government - i.e., ambivalent with regard to populist movements; (e) socialist with regard to economic affairs.
So, how many people do you know adhere to that entire spectrum of issues? Not many I'd bet. In its totality, the Catholic Church cuts across contemporary liberal/conservative lines and the ideology of its congregation tends to be much more defined by political views than religious teachings.
So, in short, I would say that it's not especially useful except in the most broad sense of identifying the religious influences that shaped one's beleifs, although whether in a proactive way or a reactive way depends on the individual, on the given issue, and on his social context.
My question/point, ineptly made as it was, is that if one self identifies as a Catholic, that reveals very little about what one believes about anything, when it comes to public policy issues that divide the American public square. Thus chatting about Catholics on the court, or Alito as a Catholic, is sort of a waste of time.
And there you have it.