The main problem with D for production is its runtime. GC,
DRuntime, Phobos is big constraint for real world software
Good D code should be nothrow, @nogc, and betterC. BetterC means
that it must not require DRuntime to link and to start. I started
Mir as scientific/numeric project, but it is going to be a
replacement for Phobos to use D instead/with of C/C++.
For example, Mir CPUID, Mir GLAS, Mir Random are nothrow @nogc
and do not need DRuntime to start/link. (Mir Random is not tested
for BetterC, so maybe few dependencies are exist.) Mir Random
covers C++11 random number generation for example.
If D code can be compiled into a common C libraries like Mir
libs, than you can include it into existing ecosystem. Currently
it is possible only with LDC (requires some programming
techniques for now).
I will be happy to see more Mir contributors 
Currently there are 5 Mir devs (not all are visible publicly).