From a quick reading of some background information on Judge Roberts, this is some early conclusions I have drawn. First of all, reliable conservative. Secondly, more moderate temperament (aka, Rehnquist style rather than Scalia style). He is highly, highly qualified to be on the Supreme Court.
While it is apparent that he is not a big fan of Roe v. Wade (he authored a brief for the Court that argued for its reversal), and despite the fact that he is being named to fill the vacancy of Justice O'Connor (whose swing positioning makes her seat all the more valuable to both sides), I don't see any reasoning for his *potential* filibuster. Even if Roberts decides one day to overturn Roe, there are still five votes to uphold it (the four of the liberal bloc plus Kennedy).
For me, a judicial nominee's most important characteristic is temperament. Roberts' has a relaxed, reasoned one and that is the type we need on the Court. So, I say he should be confirmed.