64-bit Unity Editor: What's the big deal?

I heard that Unity 5 will ship with a 64-bit editor. But I don’t understand why that is such a big deal. I’ve heard people begging for this feature. But what really is it? What are the advantages? What is its difference with the current version of the editor (32bit).

This is simple: maximum available memory. This is mostly important for building when big link cache is prepared.