Web Performance Best Practices Extension

Google has been busy this past month. They have just released a Web Performance Best Practices extension for Firefox. Via Google:

When you profile a web page with Page Speed, it evaluates the page's conformance to a number of different rules. These rules are general front-end best practices you can apply at any stage of web development. We provide documentation of each of the rules here, so whether or not you run the Page Speed tool — maybe you're just developing a brand new site and aren't ready to test it — you can refer to these pages at any time. We give you specific tips and suggestions for how you can best implement the rules and incorporate them into your development process.
Basically this tool is an extension to Firebug and has a series of rules it uses to check your web page to find performance bottlenecks. It's Google's version of YSlow, but seems to be a bit more detailed in the performance testing results and lacks some of YSlow's additional features.

Site optimization is not just for high volume sites. It’s something everybody that makes a web page should look at, for your sake (server workload and bandwidth) and the sake of your users. Google has added another tool to help you find and address performance issues, so I highly recommend giving it or YSlow a look.

*Be ye forewarned - I’m getting some errors with this extension on Firefox 3.5 beta (Google explicitly says it doesn’t work with the betas).