I never used them before, but I do use them in RMU, as I find the system a little easier to use. However, instead of rolling for breakage on a roll of 33 or 77 (which my players and I sometimes forget), I roll for it on any fumble. It makes fumbles potentially worse, but at least I remember to make the checks.
I have found that breakage does add something to the game. It provides a sense of realism, and makes crafting skills more valuable. To add more value to crafting skills, I also encourage players to not just repair but also craft their own gear, for a discounted price -- they just buy the raw materials and access to a forge for a few days.