Just a heads up, OpenDNS blocks your domain for "Web Spam". You might want to poke around and make sure you don't have unprotected comment forms or open redirects.
I don't mean to start a flame thread, but people moved away from Apache precisely because it's too heavy and slow. Nginx should work much more smoothly, unless there's some dynamic backend bottlenecking instead (and even then, Nginx' buffering frees up the backend faster).