The slides from my PHP Quebec talk on "Common Optimization Mistakes" are now up and can be downloaded from here:
http://ilia.ws/files/phpquebec_2009.pdf
I am pretty happy with the talk, which was a bit strange for me, since I get to talk about some of the downside of optimizations, rather then talking about the various specific optimizations. It looked like the audience liked the talk (I hope), so the results seems positive