For those annoyed that this just focuses on colours, here's some C++ features of VS2011:
C89 is good enough for writing device drivers, the only place Microsoft still advises to use C instead of C++.
As for C99 support it is not as if Microsoft would be the only one not supporting it.
http://en.wikipedia.org/wiki/C99#Implementations
To be honest I think C99 and C11 will most likely go unnoticed by all major compiler vendors.
Have you validated what 'mostly' means?
Let me tell you that each compiler manufacturer has a different dictionary to look up the meaning of 'mostly'.
If a standard is not 100% implemented across compilers, no one can be sure to use it if portability is a concern.
This is exactly like the time where most databases 'mostly' implemented the SQL '92 standard, and then the code had to be full with DB specific workarounds.
Have you? Real question - I'd be very interested in that.
The list of (allegedly) fully compliant compilers is not very impressive (IBM, PGI, Sun), but in practice, you're aiming at C99 support to the level of GCC, which will get you - in addition to GCC and its (supposedly) drop-in replacement Clang - AMD and Intel (I think ICC has C99 support to GCC level, but there are probably discrepancies in the feature sets)...
So it might be not that easy for certain companies to use your suggestion.
As far for what 'mostly' means. I have been coding since the K&R days, so I am aware that even when things are supposed to be 100% the same among C compilers, reality speaks otherwise.
Also, MS doesn't really have a good track record of backporting C++ features to C (mixing code and declarations, anyone?).
If you want to write portable C code that works on at least *nix and Windows, either ignore MSVC (GCC works just fine on Windows via MinGW or Cygwin cross-compiler, as does Clang once you get it set up), or restrict yourself to the common subset of C99 and C++98...
int whitespace[256]
= { [' '] = 1, ['\t'] = 1, ['\h'] = 1,
['\f'] = 1, ['\n'] = 1, ['\r'] = 1 };