We started using the Failure Stunts in our last session, during the Oleander Maw. The room the players were in was set on fire, and we justified the characters' Permanent Damage with elements in the room catching fire, them tripping into burning debris, or collapsing pieces of flaming room falling onto them. All but one of the party members received permanent scars because of it.
We use both charts and when a fumble is made, they roll a separate d6 (evens using the "good" chart, odds gets you the "relishing failure" chart).
At first the players were outraged at having to scar their characters for life, but I explained that this isn't some happy-go-lucky fantasy D&D game -- its supposed a more serious, dark
RPG. You *will* get hurt, and there should always be a sense that you won't make it through the campaign. It brings in a more realistic atmosphere wherein, if you fight in a burning room for 12+ rounds, you're going to get badly burnt!
Those failures really helped in finally bringing that point home for my group. I'm in no way an "evil" GM, but in that light, I love those failure stunts.