Looks like a cool program. I like the name.
Drosera runs in its own window and provides most of the debugging features that you would expect. This includes the ability to step through code, breakpoints, a command console, and access to the variable and function stack.
The Drosera page states that it is not currently available on the Windows platform, but it was available when I downloaded the nightly build on Feb. 2, 2008. Drosera has a way to go to compete with Firebug, but it does offer a usable tool.