I also mostly use C, and also consider C++ a monster with too many quirks.
C compilers are virtually available for any target, are robust.
I mostly do embedded dev these days though as far as programming goes, and otherwise a few command-line tools. I used to write GUI apps in C in the past, very rarely these days, although I have written a cross-platform GUI library in C based on OpenGL which allows to write cross-platform GUI apps in C in a decent way. Not too shabby but I wouldn't want to spend my whole time doing this anyway.
My use of C is pretty object-oriented though (at least in the base concepts of OO), and with C properly used and mastered, I've never really found C++ to add much convenience for that overall. Of course, YMMV a lot.
C++ is too complex IMHO, and promotes a kind of OO programming that can yield monster code bases that can be very hard to evolve. Badly used inheritance, for example, can make your life a hell in the long run. Of course this is not specific to C++, it's common with many OO languages that support multiple inheritance. Another pitfall with C++ is that in practice, it's a very "fragmented" language, because it's so complex that most developers tend to use their own subset. Lastly, C++ compilation times are much longer than C compilation times, which granted is not that important, but that's an additional benefit of using C in my eyes.