D doesn't have a bombastic or killer feature. What it has is elegance. It simplifies things, and smooths out the ugly stuff. You don't have to worry if your char is signed or unsigned, or how many bits are in an int, or whether to use dot or arrow, or remember to make your destructor virtual, and on and on.

It's a more memory safe language than C/C++, no need to worry about forward references, strong encapsulation, simple modules, and so on.

And let's face it - the C preprocessor is an abomination in modern languages, why does it persist?