But for developers it was always hard to debug and inspect your web applications running in Safari. With Drosera a decent debugger exists since June 2006 (for Webkit only so far, though — it's not going to happen with Safari 2).
And now, the (already existent, but somewhat weird looking) (Web) Inspector got a makeover:
This is a big step, giving web developers not only the chance to precisely identify why this or that DOM element is shown in the way it is, but it also allows a look into how the web page loads, much like Firebug on Firefox.
As a neat extra, you can view how your components add to the loading time of the page.
Even though Webkit is in some ways just mimicking Firebug, it is a good step for future web development on Safari. Even more as the new Webkit builds contain less than the usual number of browser quirks that make programming Safari difficult in the Ajax world.
Finally one more pic, because it's quite beautiful :)