I think Roberts IS a conservative. A cautious conservative, for sure, but I think we will find he's pretty solid when he's on the bench. And, I think his opinions will be well thought out and articulated. He may have more respect for precedent, however wrongly decided, than we might like, and that is a concern. From the recent Coulter article, what paper trail Souter had, he sounded conservative, so one never knows. We just have to trust W and his team on this one.
Let us not forget, Roberts will not be President Bush's last SCOTUS appointment, either. Certainly Rehnquist won't be sitting there another 3 years, and I find it hard to belive Stevens will. (hopefully, that's not wishful thinking)
I agree that I do not wish harm on any justices. Some of them though, deserve to retire, go on book tours, go abroad and read interesting rulings from foreign courts....
My main point is that when Bush really wants something (CAFTA, NCLB, Prescription drugs) he gets it done. I find it hard to believe if he wanted to appoint someone who was unambiguously conservative, he wouldn't do it and fight.