This is D2 - I don't use D2 and wouldn't use it. I was talking about D1/Tango combination. I don't think I'll make a switch to D2.
"Is the output binary as good as a C++ one? That would be my first purely technical concern."
That depends on the compiler/linker, of course. In short - dmd good enough, ldc great (llvm as the backend after all).
"Other concerns would be related to the building tool chain and the quality of IDEs."
You can download DMD/Tango package from their Trac page and you're ready to go, however I would strongly advise you to use SVN tango version - which implies you need MSYS(on Windows) to build it. Ask for help on forum there (dsource.org/projects/tango) or on irc d.tango (freenode). As for IDE, you can use Descent for Eclipse, as some people do. I use Emacs for everything though, same applies for D - there is a module for it.
"But the real concern is business oriented."
There is no concern here, since basics of risk management should tell you not to use it. Same applies for other emerging or obscure technologies as well (I'm looking at you Lisp). Short answer, don't use it for business critical things yet, though some have done that with success.