I'm leaning that way, too, but this would have been a ground-breaking decision no matter which way it was decided. The main reason that I think I support the decision is because I'm uncomfortable saying that the states may tell consenting adults what particular positions are acceptable and which are not. I'm all for states' rights, but putting the government at any level in my bedroom is not exactly a good idea. They'd learn far too much! ;^)
The drawback is that gays marriages are now FAR more likely to be supported, since it uses the same logic: consenting adults of the same gender should be allowed to do the same things as mixed gender couples. A very strong, simple, and supportable Equal Protection argument.
Had the Court gone the other way, I would have been happy that states' rights were starting to be respected more, and would have been hopeful that it would be a trend for the future. I need to read the dissents to get more insight into why this decision is a bad one, though, because I trust Scalia, Thomas, and Rehnquist far too much to think that this is the only thing that was lost today.