I reside in the city that started Earth Hour - Sydney.
Having said that, there are years that I have embraced it and years that I have supported "Human Achievement Hour" (which occur simultaneously).
I have recently come to the realisation that while Earth Hour itself has little benefit for the planet, the symbolism itself is a marker for the brain. It brings to consciousness, the affect humans have on the planet. This could (but probably won't) change behaviours.
The original focus of Earth Hour was to have offices turn off their lights to demonstrate the waste of energy. While the offices claim that security is the reason for leaving on lights, the true reason is energy pricing and the discounts that come with higher usage.
While it may not be in the best interest of a business to reduce energy consumption, I do believe, whether or not one supports the concept of climate change, that the reduction in energy usage through minimal behavioral changes while retaining functionality should be often brought to the forefront of thought.
As such, I now observe Earth Hour like I would a moment of silence.