Just began looking at this one last night. It's available, with source, from Digital Mars (http://www.digitalmars.com/d/2.0/), and it's quite interesting.
It is definitely a general purpose programming language, and addresses many areas where people want to pull out their hair with C++. It seems it can directly compete with Go (Google's programming language), in the areas of concurrency, has a system of generics and is what I would call a "more than complete" language :-).
It's actually pretty big, and many people might claim that you don't have to understand what you don't use. That's only true if you're the only one authoring code in this language, or have a set of restrictions to a subset of the language that you go by.
Go, on the other hand, is pretty small, and fairly simple. One can understand the entire language fairly quickly by just reading the specification. It's quick to learn, the tools are quick, and the code runs reasonably fast.
D2, at least with the Digital Mars compiler, is pretty fast too. It can be executed as a "script" of sorts, making it nice for system administrative tasks where you often need the source to be right there.
Both languages seem to do quite well at achieving their stated goals and philosophies, and I expect them both to become more important to know as time goes on.
I hope to see both grow in popularity in the not too far off future.