Is it my imagination...
or did the Supreme Court's term end with an awful lot of identical 5-4 splits? It's not just that O'Connor switched sides often enough that you might get some 5-4 liberal decisions and some 5-4 conservative ones. It's that there'd usually be a few significant cases that turned out to have 6-or-more-person majorities. The past couple weeks seems anomalous to me in recent-historical terms. The five conservatives hung solidly together as did the four liberals, with no interesting defections except for Kennedy on the death penalty, across an especially wide range of cases.
Update Stuart Benjamin says something similar. He thinks it's unusual that an antitrust case followed exactly te same 5-4 roght-left cleavage as constitutional cases, and that the majority and minority are now engaged in ideological "shadowboxing" even over cases that aren't directly ideological.
Eugene Volokh reports that Kennedy was in the majority in all 24 5-4 cases this term-- he is now the swing vote, with the other 8 dividing the same way over and over again. Overall Kennedy was in the majority 69 out of 71 times.
But Kennedy did swing back and forth a bit: "Note that the 24 5-4 cases came out with Kennedy joining the four conservatives 13 times, the four liberals 6 times, and no easily identifiable bloc 5 times."