I understand that this is a LAMP forum, and Ruby on Rails (RoR) may be considered off-topic, but I think this question is on the minds of most of us who are evaluating RoR vs. PHP for high-traffic Web2.0 applications. I also consider you to be highly competent and objective.
Given that things like caching, SQL tuning etc. are more important to handle high-traffic than the actual page-generation, how slow do you think RoR would be compared to PHP? Also, you talked about the performace differences between different database drivers for MySQL/PHP. Could you comment upon MySQL/RoR choices?
Thanks in advance,