I've upgraded to to nginx 1.4, and added spdy to my listen parameter. It works when I access the sites via https, but if I access via http then I get an 'internal error' Remove spdy on the :80 listen parameter and it works fine again.
I first need to resolve why my site looks all wrong with https, it's as though CSS isn't being loaded or semething. Would CDN also work if you use HTTPS? Perhaps that's my issue?