Generally, I prefer mainstream languages myself, that’s why I mostly code C++ and C#. But “generally” is the key here. For some projects, or some parts of it, picking a non-mainstream language can be a huge win in terms of productivity.
I never used D in production, but I can remember several occasions where I picked unusual languages, both specialized and general purpose ones. Among others, I’ve used XSLT, sed, awk, VBScript, VB.NET, R, power shell, AutoLISP, MATLAB.
Theoretically all modern programming languages are equivalent because Turing-complete. Practically, for a particular problem, it can be orders of magnitude difference in development time between them. The reasons include availability of specific libraries, integration with other code be it third-party or legacy, or specific runtime features.