Planned Parenthood already opposes him "because he would undermine basic reproductive rights." Remember that Planned Parenthood didn't formally come out against John Roberts until well into the confirmation hearings.
NARAL says, "In choosing Alito, President Bush gave into the demands of his far-right base and is attempting to replace the moderate O'Connor with someone who would move the court in a direction that threatens fundamental freedoms, including a woman's right to choose as guaranteed by Roe v. Wade."
Jim Geraghty at TKS nicely rounds up my thoughts:
I think that at this moment, many, many conservatives, confident that the American people want judges to be judges, and not legislators, are stretching, flexing their muscles, and pounding the chest, whispering menacingly, "Bring. It. On."