Awesome! Had the Death Star not been destroyed at Yavin, that means the Rebellion would've been crushed within three months.
I don't know about that- Mon Mothma, Commander Ackbar, Crix Madine, and several other major Alliance leaders were not at the Yavin base, so the Rebellion would not be in total disarray. Also, if Yavin was destroyed and the Death Star survived, a few elements of the post-Yavin war would have gone differently. Darth Vader would not have been given a massive fleet to crush the Rebellion, as the victory would have made the Imperial Command more complacent rather than vengeful and motivated. Also, if the Empire started using the superlaser in earnest, the entire galaxy would have rebelled; just the destruction of Alderaan, which had been effectively buried in propoganda, had nevertheless caused a rash of Imperial desertions- imagine what would have happened if the total destruction of worlds became doctrine! All ethical Imperial officers would be placed in serious dilemmas and every planet concerned with its own survival would basically be forced to declare war on the Empire as a preemptive defense against the Death Star.
Forgive me if I'm waxing lyrical- I've just read two World War Two theorists' books and am feeling a little anylitical right now.
Still, it's fun to speculate.