This app was demo'd at Google IO this past spring. It was incredibly cool back then, and it's only gotten better since. It's going to be an amazing tool for web developers.
I think this is what Yahoo! wanted that YSlow firebug add-on to be. I'm quite enjoying Speed Tracer but it's giving me a warning about Google Analytics embed code. Those two teams need to have a meeting..
I haven't dug into it yet, but from the video the sluggishness and network graphs seem to be a great level of abstraction at which to view the UX behavior of your application.<p>One question I have: I can't figure out if this is only for GWT (Java compiled to Javascript) apps or for any web app). Anyone?
This would be even better if it could break down javascript execution time on a line by line basis. I was able to spot an inefficient javascript file, but only found the culprit by commenting and uncommenting lines (inefficient jquery selector).<p>Way cool though.