Above is a link to a story regarding the Free Fight missions from No More Heroes that goes into detail about if these are really frustrating or enjoyable to play with the system that is set up in the game.
For me, when I'm playing the game it is easy to just go do one of these "fights" when I feel like it and it is not something that feels like it must be done to get anywhere. Yes they can be difficult but once you know the pattern of how the enemies attack, you will have a much better chance of surviving the mission. If you fail, then the mission just disappears from the map until a later time when you can try it again. So even though a "retry" option would have been nice for some of the missions, at least it doesn't force you to continue to keep doing them over and over again.
How do you feel about these missions?