D Programming Language in the real world?

I'm using D for my research work in the area of computer graphics. I and others have had papers published in our fields based on work done using D. I think it's definitely ready for use on small to medium sized research projects where performance matters. It's a nice fit for research work because often you're starting from scratch anyway, so you don't have much legacy code to worry about integrating with.

Another popular area for use seems to be web services. Hopefully someone else can comment who's in this space, but there too I think the idea is that performance often really matters so you want a compiled-to-the-metal language. Services are often fairly small, self-contained processes, so interop with large amounts of legacy C++ code is not really necessary or useful. Thus D can get its foot in the door.

I think D will continue to gain grass-roots followers in this way -- on smaller projects that for whatever reason can afford to ditch the C++ legacy in order to gain a programming language that's much more enjoyable to use, and perhaps more productive too.

But until there's a huge number of grass-roots users there won't be much in the way of big corporate users I suspect.

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.

I use D for web development and it proved quite a lot more productive compared to C/C++. There are a lot of frameworks based on ruby/php/python, of course. But when you want to develop something unique that also have to be as fast as C and nearly as easy as to program with as you do in many script languages, then D is a good choice.

I know of one smallish company that have sent a mail server product to the market. They had at least 2 people working full time on the project.

Also, a major player in the IT business have several employees using D in larger internal projects.

Further I know of one company seeking venture funding, several (at least 4) employees in smaller companies using D either part or full time, and at least a couple (including me) actively seeking opportunities in the consulting market.

I've probably left out a few that I should have known about, and probably some I haven't heard about, but that still exists, as the above is more or less those I know myself via the community.

A small percentage of my current income comes from D.