Kennedy's opinion made an excellent argument for gay marriage as being a good thing, while being generally respectful of the other side.
However, I was looking to be convinced by him that there was a Constitutional requirement for gay marriage to be recognized, and he didn't do it for me. Roberts is right that he sidesteps the foundational question of how marriage is defined and who defines it. The dissents did a pretty good job I thought of arguing that the majority's opinion was based on a very far-reaching understanding of the Court's role when it comes to substantive due process.
I haven't read the opinions yet, but I get the same feeling. I'm really curious to see the detail of the arguments on both sides.