Nope, it was David Strauss who was experimenting with kargo-event (now called Kellner) at https://code.launchpad.net/~fourkitchens/pressflow/6-evented but I doubt anything serious came out of it.
Drupal 7 does have a lot of bootstrap already cached, there's a cache_bootstrap bin for that. You can stick it into memcached.
You can go overboard and decrease code loading with moving some / lots of Drupal code into C. Damien and dhthwy created PHP extension at http://drupal.org/project/drupal_php_ext not much is done with it. Or do hiphop. I do not know the current state of hiphop & Drupal 7.
At the end of the day, however, you need to take a good hard look at the engineering costs of, say, getting hiphop work with Drupal 7 (and all the contrib!) and compare it with renting a few more servers. If you can save, say 5% of your servers and you have 100 000 servers, go for it, but are you Facebook? Be careful and economical with optimizations.