The slides (http://talks.php.net/show/dojo/1) seem good as a quick overview of the talk. The take home messages generally being: make sure you know where your application is spending its time using strace, and to track superfluous overhead (such as configurable fallbacks that you can hardcode in a deployed application). Also: HipHop is not a magic bullet. Without heavily computational application code it gives only marginal improvements over PHP with APC, at least in these tests.
Yeah it's mostly the kind of micro optimization stuff that really isn't going to be to large a percentage of your time in a web app, assuming that you are probably waiting on queries. Then when it does really matter your probably at the scale where you want to ditch PHP for the specific stuff you are doing that is CPU bound. Kind of like Twitter is having to do with Rails.
He optimizes stuff he thinks is expensive and then runs the profiler to see what's expensive and then ends up saying "If you don't know what things cost, you are lost." Seems someone needs to take their own advice.
Based on the slides, did not have the patience to wait 10 minutes for the vimeo video to load.
