First the good news:
As most gay people in the U.S. are already aware, the Iowa Supreme Court unanimously declared Iowa's defense of marriage statute to be unconstitutional on equal protection grounds.
Further a Proposition 8 type backlash in Iowa is unlikely because Iowa has properly stringent procedural requirements to amend the state constitution. There are only two procedures, the first is that the amendment must pass both houses in two consecutive legislative sessions, and then be approved by a majority of voters in a general election. Unless the democratic Iowa legislature passes a Prop 8 type amendment in the current session, the earliest such an amendment would appear before voters would be 2012. The second is via constitutional convention. In 2010, the voters of Iowa can vote to have constitutional convention, and if they so vote, in the following session (beginning in 2011) the legislature determine when to have such a convention.
Either way, there is good amount of time for the citizens to realize that allowing gay marriage does not lead to rampant bestiality, polygamy, child abuse, and whatever else the gay marriage opponents pretend to worry about.
Now the bad news:
It is still likely to galvanize efforts in other states, perhaps making marriage equality across the nation more difficult to achieve. Outrage will be directed towards "activist courts," and states without marriage amendments are likely to see a push for such. States with marriage amendments that allow for the possibility of civil union may see a push to explicitly prohibit civil unions, perhaps even to the Virginia extreme.
This is a battle won, and an encouraging one at that, but the war continues.