Bummed for the Americans who were denied service for no good reason.
In other words, nobody.
As for the Americans who were denied service for a good reason, it's because Americans have a right to free exercise of religion. Whether somebody disagrees or not, the religious texts followed by Jews, Muslims and Christians are at least in part hostile to homosexuality. That makes it a complicated issue: an explicit Constitutional right (free exercise) versus another Constitutional right (equal protection based upon orientation). One doesn't -- and shouldn't -- automatically outweigh the other.
As for the ruling itself, it's a fairly narrow one. Rather than saying that religion trumps, or that free speech carries the day, it simply finds that Colorado's decision in this case showed open hostility to a religious defense, which the government is not allowed to do. Kagan / Breyer wrote a concurrence in which they indicated their belief that a fairer process without such hostility may have resulted in the same decision (i.e., that the baker had violated the law). The majority opinion is silent on that point.
But, there are all kinds of implications for cases like this, and I intend to agree with JSD: business owners shouldn't be required to violate their religion. Should Muslim caterers be required to service pig roasts? Could a devout Mormon wedding singer refuse to perform at a drag wedding?
I think, too, there's a difference between providing a service available to everyone -- selling a cake in the display case -- and requiring somebody to provide custom services, such as designing a cake for a gay wedding and personally inscribing the cake. The latter covers the situation in this ruling. Requiring somebody to participate in a practice that violates their religion just seems wrong.