L.D.
My children are 20 months apart - now almost 3 and 14 months, and they share a room. They HAVE to because we only have two bedrooms, but If we had three, I would still keep them together.
For the most part, they sleep through each others noise - which is remarkable because my daughter gets up and hollers in the night, and my son hollers when he goes to bed (when my daughter is already asleep) - but they are used to it, and just keep on sleeping.
I like having them together. i think it helps them feel close. The other night, my daughter was crying and my son came out and told me she was crying. When I went in to get her, he was in her crib with her, singing to her, and had given her a stuffed toy.
I like the idea that they are together to keep each other company and take care of each other.