A hard reset would have been useful last night when I made a sketch that was continuously outputting text to the serial without any pause.It seemed to freeze up the IDE when I tried to use it with the Arduino connected and made it almost impossible to try to upload a new sketch.
I finally succeeded with some combination of unplugging the usb and hitting the reset and trying to upload. Really frustrating experience. I've learned to never do that again.
Don't try this unless you are prepared to risk bricking your board completely!