I have two girls that are 30 months apart, and they do share a room. It's been the best decision for our family. When they were very young, like yours are, it helped because they encouraged each other to go to bed, and they kept each other from feeling lonely. Now that they're older it's still very good. They do play at times, and keep each other up, but usually it works for us, not against. Now I think they couldn't sleep apart- or at least it'd be hard for them. They're so accustomed to each other's night sounds that I worry if it weren't for that, they wouldn't sleep.
They are close, my girls, and I do think it has to do with sharing a room. We treat them like a pair, and they're used to being treated that way. We sail past fairness issues for that reason. They're close enough in age that what one can do, the other can too, and what one cannot do, the other can't either. And it sure makes bed-time stories go smoothly.
The hardest part is their clothes! Sheesh- that is the single biggest challenge for us. Not even the toys are as hard to keep organized, but I figure it's a small price to pay.
Best of Luck with your pair!
J.