I can only give you what my gut is telling me, and of course, his influence on the more moderate tone of Bush's re-election campaign messages. It seems to me that Rove picked Frist for a reason, and I don't think it's because he's a pillar of conservatism. Of course, I am not too familiar with Frist so we'll see.
Then again, I am not a Rove fan, do not like the influence he has, and wish Karen Hughes was more heavily involved.