It's been a long day of perfunctory paeans to Sandra Day O'Connor's many virtues. Some corners named her prudence and moderation, smarter corners lauded her "mainstream conservatism", but few said much about her. So before we all move to the looming battle for her seat, it's probably worth listening to Ogged and talking a bit who she is and what made her important (full disclosure: the biography aspects are taken from wikipedia and much of the judicial analysis comes from Rehnquist Justice):
O'Connor's a Texan, but she spent her childhood on a cattle ranch in Arizona. From there, she nabbed a B.A in economics from Stanford, and continued on in their law school. She graduated in two years, rather than the three favored by most mortals. Third in her class, she came in only two spots behind the valedictorian, one William Rehnquist. Not a bad record (and one beautifully retold in Dahlia Lithwick's article on O'Connor's many firsts).
Bad time, however, to be a female lawyer in America. Despite her killer academic performance, no firm in California would hire her on as a lawyer (though one enthusiastically offered her the position of secretary). Instead, she went into public service, becoming Deputy County Attorney for San Mateo, CA and Assistant Attorney General of Arizona. From there, she was appointed to the Arizona state senate, won reelection twice, and became the first woman to serve as senate majority leader in any state. In 1975 she was elected judge of Maricopa County, then appointed to the Arizona Court of Appeals, and finally to the Supreme Court, fulfilling Ronald Reagan's campaign pledge to nominate the first woman to the body.