I just tried this. It has a lot of overlap with YSlow, but there are some interesting extra rules in it, most notably a rule that finds inefficient CSS selectors. That's kind of cool.
Was I the only person who was a little surprised that they didn't mention YSlow by name? That strikes me as somewhat rude, though I know Yahoo and Google aren't exactly best buddies.<p><i>Edit</i>: Looks like some of the commenters there agree with me on that point.
One annoying thing with this thing is that it creates a bunch of dirs in your home dir and dumps stuff in them when performing the analysis. Shouldn't they put things like that in /tmp, if they need to store them at all?
It looks really useful. Much more than Yslow, and Yslow is great too.
I posted an example <a href="http://dodeja.posterous.com/762803" rel="nofollow">http://dodeja.posterous.com/762803</a>
It even gives images that are optimized and JS that is minified. Developers <3 Google
I also liked the specific action items. Like which exact css selector is inefficient. Also liked it called out the exact images that could do with compression, what % can be gained and even a sample compressed image!
You may also want to try this: <a href="http://www.webpagetest.org/test" rel="nofollow">http://www.webpagetest.org/test</a><p>Pretty charts, and pretty good diagnostic.<p>(Health warning: knowing how much junk is spewing down the wire from some sites may turn your stomach ...)
Wouldn't it be interesting if Google started applying a bias to search results, pushing fast sites up the list?<p>I would definitely appreciate that option. I <i>hate</i> slow web sites.