To me, Stare Decisis is judicial laches. To the extent that the affected public (my phrase) has come to rely on a proposition as settled law, it would be disruptive to reverse it because it has come to be viewed as erroneous from the outset. Otherwise, there would be no predictibility of a legal outcome and people who want to act within the confines of the law would have a harder time doing so.
In my own opinion, if Roe v. Wade were settled law to the extent that stare decisis clearly should be applied, then the Democrats on the committee (and Specter) would not be so frantic in trying to extract a commitment not to overturn it.
On the other hand, the securities laws, to name one area where stare decisis is important, are filled with made-up interpretations that have come to provide a settled and predictable model of outcomes, which securities practitioners can use to plan their own behavior.
It's a little different when talking about statutory law, because Congress can change it at any time if the court gets it wrong. Constitutional law is a whole different ballgame, because it's not meant to be constantly amended. It's meant to provide a stable framework, and so if stare decisis becomes too dominating a factor, it effectively means that the courts have the power to change it on their own, and that undermines stability, rather than promotes it.