how it works: you get 2 icons in the status bar (which you can move to another bar :-) to set the debug cookies
it works perfectly with eclipse (probably netbeans as well)
-0.5.1 redone the interior -> code simpler/more readable
-0.4.1 on tab change / reload the icons now show if the cookies are set or not
-0.4.0 you can set different cookie values/names/timeouts in the preferences ( addon manager->easy debug (with moveable icon)->preferences )
for it to get working you need to install xdebug and configure it do do remote debugging (it the steps at the bottom dont work for you try google with something like 'eclipse xdebug remote debugging')
when its working you can debug any php file you view in your browser on your localhost. The cookie (when set) tells xdebug to do the compiling and eclipse (when started) hooks into xdebug (send it the breakpoints you define) and gets the live data (and pauses the run of the script while you debug)..
you can walk through the code line by line, jump to breakpoints and even manipulate the variables on the run.. they did a great job!
this extention just helps to make the process smoother..
on ubuntu to enable xdebug i only needed the following (no garantie it works for you):
sudo apt-get install php5-xdebug
File - New Project - PHP Project
Name your project
Choose Create project at existing location (from existing source) and browse to your Magento root folder (as used by xampp)
Hit Finish and wait for the project to create
Set up xdebug as your debugger in eclipse
Window - Preferences - PHP - Debug
Change the PHP debugger to Xdebug
Set Accept remote session (JIT) to localhost - OK
Apply - OK