Or is it the key signature of C? Tonality is such a luxury when writing music, but I find that the music I write drifts from one tonality to another at a pretty fast rate, and I have to throw all rules of traditional harmonic analysis out the window when deciding if a note should be a G sharp or an A flat, especially if it is going to an odd place. (And what is the point of using tonal harmony if you can't be creative with it anyway?) When push comes to shove (or once the bowing and blowing starts), what matters is how little thinking a musician needs to do in order to get from one note to the next in order to play it comfortably and in tune.
I have found that most orchestral musicians (including myself and excluding competent pianists)
1. don't give a fig about traditional harmonic analysis
2. prefer to be comfortable, both mentally and physically, when they play
3. like to have parts that sound resonant on their instruments
4. like to be able to hear what's going on around them
Wind players prefer flats
String players prefer sharps
Everyone hates double sharps and double flats
So in my current drift through the enharmonic sea (working on a piece that does not include piano) I'm taking the ride easily, and I'm not going to worry about anyone's analytical thinking. It is very liberating. Imagine what would have happened if our friends in the Neue Wiener Schule had relinquished their worries about analytical thinking rather than the need for tonality at all?
I think that the next time someone asks me what kind of music I write, I will tell them that it is "enharmonic."