It is kinda early to tell, but this decision does provide some hope that maybe Alito will be a suprise to the right.
As far as the practical implications of this, I still think the democrats were cowards for not fillibustering the Alito nomination (and I think at this point unfortunately are showing that the GOP may very well prevail in ’08… I can’t believe it, but they have dropped the ball so badly and resoundingly it is staggering… they could have eaten Bush alive on Abu Gharib, the domestic spying scandal, the SCOTUS appointments, the lies that took America to war, yet they just keep rolling over — why would American voters choose Democrats where is so little practical differenced between them and Republicans), but that said it looks like the actual effect of this appointment may not be the tidal change that folks seems to be expecting.
The two justices who are now gone Rehnquist and O’Connor were a hard-right conservative and a moderate respectively. The two new justices are hard to feel out. My guess is that they are conservative but will tend to be more likely to respect State Decisis than say say Scalia or Thomas. So assuming that both are somewhere between O’Connor and Rehnquist in their philosophies, then I think the net change is likely insignificant. Individual cases of course are up for grabs (my guess is that the partial birth abortion ban will stand if health exceptions are provided, but Roe/Casey is safe), but the general direction of the court will not change that much.
That said, SCOTUS was already a mess and is in my opinion a huge source of oppression in this country, by refusing to stop many of the abuses of the criminal injustice system (including the legalized lynching system, a/k/a the racist death penalty in America), the tyranical abuses of Presidential power, and the suppression of voting rights. So anyway things may not get much worse, but that’s not saying much. America still only provides justice for rich white people. Poor folks of color are still being deprived their true day in court.