I feel you guys are straying from the topic a bit. Synesthesia is an incredibly rare occurance, and so far it sounds like somehow this forum is an absolute magnet for it, how extraordinary!
I'm with Paul here, There are mad people, there are creative people, there are mad and creative people. Fuck my psychiatrist diagnosed me with Seasonal Affective Disorder this past winter, it sure as shit has never seemed to help me with my creativity. And this is from someone who wishes they were creative, I want to be a writer, but if anything having any sort of condition where you're down all the time, well, it doesn't make you want to write, it just makes you want to, you know, lay there and not do anything.
I can see things like Asperger's being a boon in disguise though, anything that basically forces your brain to stay on one subject for long periods of time and you're eventually bound to think of something new and exciting about it, after the long and exhaustive hours of work that is. Creativity is just like any other pursuit, it takes time and work if you want to come up with anything spectacular and beautiful. I'm saying this from the angle of being an enormous procrastinator, seriously, I could be writing poems right now for one of my classes, I just spent 3 hours playing Banjo-Kazooie: Nuts and Bolts and then hopped straight onto the internet.