I do bioinformatics work in D. For me, the key thing about D is that it takes a very level-headed approach to tradeoffs and recognizes the principle of diminishing returns.
Unlike C++, which adheres rigorously to the zero-overhead principle, D allows features that may have a small performance/space cost if they make the language a lot more usable. These include garbage collection, a monitor object for each class, runtime type info, etc.
Unlike Ruby, Python, PHP, etc, D tries to be almost as fast as C, even if it is less dynamic and slightly more difficult to program in than scripting languages.
The result is a language that is optimal when both development time and execution time matter about equally, which in my field is most of the time.
Similarly, D takes a very level-headed approach to safety vs. flexibility. It assumes that programmers basically know what they're doing, but do make mistakes.
Unlike C and C++, it assumes that you don't want to use pointers, unsafe casts, manual memory management, etc, everywhere in your code, because they're error prone, and assumes that you don't want to sift through multi-page template error messages when you screw up just to use resizable arrays.
Unlike Java and other bondage-and-discipline languages, D assumes that sometimes pointers, unsafe casts, manual memory management, etc. are a necessary evil, and assumes you're smart enough to handle real templates, operator overloading, etc. without writing obfuscated code. It also assumes that you may screw up and access an array out of bounds, but that the programmer knows best what tradeoff should be made between safety and speed in any given situation. Therefore, whether arrays are bounds checked is simply determined by a compiler switch.
