That's an excellent feature. the scenes in unity are binary and not merge-able. That feature alone left me considering other options when I was looking at game engines.
I am legitimately surprised they're using a binary format for scenes. That is very anti-source control in general. The only binary blobs in the entire project should be assets (e.g. textures, sounds, etc). Everyone loves to whine about XMl, but I'd happily take XML for scene layout over a binary blob.
Scenes and prefabs have been able to be saved in a text format for a while. That said, they were still effectively unable to be merged in all but the simplest of situations for reasons I don't fully understand.
Hopefully this was improved in Unity 5. One of the buried release notes mentions a new merge tool for scenes and prefabs in the engine.
http://the-witness.net/news/2011/12/engine-tech-concurrent-w...