My fundamental concern is not about the decision's merits or lack thereof, but about what it says about American culture. Seventeen years ago, the Defense of Marriage Act was passed overwhelmingly (Senate totals are here and House, here). Now we are dropping a bedrock assumption of our culture because of the efforts of a small but highly influential pressure group (not because of the merits of legitimate pro & con arguments or the fundamental importance of the issue...spare me).
The DOMA decision suggests the same cultural frailty which the redefinition of 'gay' did.
It also suggests that the country as a whole does not buy the stupidity, corruption, hypocrisy, incompetence, and lunacy of the GOP's
Somewhat OT: Back in '09 I described Meghan McArdle's discussions of gay marriage as classic. Those links no longer work, but the material is archived here and here. Maybe McArdle got tired of paying server costs for her defunct site, or maybe her views have evolved.
Also somewhat OT: I'm for civil unions. When the country is divided on an issue, except in very exceptional circumstances I favor keeping the feds out as much as possible and leaving the matter to the states, or to the people. However, this post is about the cultural implications of the SCOTUS decision, not about the issue itself.