The Supremes did not flatly rule in favor of same-sex marriage, but they did say a state ban on it is unconstitutional and a same sex couple wanting to marry can go to a number of states--13, I think, including now California, the most populous, to do so.
The Washington Post seemed to have it about right: "Sometimes the Court makes history outright,...Other times it moves more deliberately, facilitating changes already underway." I expect we won't see great, sudden changes from these decisions because, as the Post noted, the changes are already happening.
Reaction? Critics of same-sex marriage booed, practitioners cheered. I like a woman quoted as saying, "When we heard the news, the family started crying with happiness, except the babies. They slept right through it." I hope they prosper.