Self-promotion, two articles I wrote on the subject: "I'm a designer who learned Django and launched her first webapp in 6 weeks" http://www.limedaring.com/im-a-designer-who-learned-django-a...
"How to thrive as a solo non-technical founder" http://weddinglovely.com/blog/how-to-survive-as-a-solo-desig...
I posted this mainly because it was an appropriate parent story, not because I think winter cofounders should do accelerated dating.
I've thought about applying as a solo-founder (knowing the caveats), but may just continue to use my spare time to flesh things out and target Spring 2013. Assuming a wet winter, that is a good time for getting some serious coding done -- less distraction to want to be outside.
It's probably next to impossible to get early feedback on a YC application but there's now one more way to turn impossible to possible: http://lookapinky.com
That said, be inspired to try finding a cofounder now, work with them for a few months and keep S13 in mind — it might all fall into place by the time the next round comes around. And if you can't find a cofounder, don't be afraid of being persistant and just learning the skills necessary to build and launch startup solo, since a great cofounder is likely to come along if you already have an intriguing product launched.