Flash Builder 4 has some nifty new features, and I'm glad it's finally released. One of the new features that I forgot to try out (until today), was using a conditional breakpoint.
To make a breakpoint conditional, just right click it and choose "Properties". Doing this, however, can dramatically slow down the execution of your code, if your breakpoint is in a method that gets called frequently.
This is somewhat understandable, as the condition needs to be evaluated each time your breakpoint is reached. In my case the breakpoint was in the updateDisplayList() method of a Spark Layout class ... and it made scrolling in my List control unbearable. Fortunately, I didn't waste too much time before I realized that my conditional breakpoint was the cause!