Google is trying to speed up the web. How? By giving you a tool to see why your web pages are so damned slow. Google penalizes you for slow load times already, so there’s already incentive to be as quick as possible, now it’s just gotten easier to get the speed you need.
So, check out PageSpeed, a Firefox addon. It requires FireBug, which you should already have in your toolkit—it’s indespensible for bug fixing and for reverse-engineering someone else’s code, like a WordPress theme. Anyway, good luck with the SEO gaming!

