Actually it occured to me while writing the above that the amount of heat released per mole of material probably isn't the best metric to use anyway, because there is a lot more mass in one mole of some materials than other. The amount of energy liberated per mass would be a better metric in my view. Consider that the combustion energy per mole of alkane climbs quite quickly as the number of carbons increases - this isn't because higher order alkanes combust more explosively or anything. It's just because a mole of heavier alkane has more combustible mass than a mole of lighter alkane. On a per mass basis, most of the alkanes have the same combustion energy (~11-12 kcal/g, because essentially the same amount and same type of bonds are breaking per unit mass).
Considering that the reaction under question gives 433 kcal/mol for the reaction of 4 moles of FOOF with H2S*, and a molecular weight of 70 g/mol for FOOF, this means that the reaction liberates 1.546 kcal/g of FOOF consumed. Compare that with acetylene, which liberates ~11.5 kcal/g of acetylene combusted, and it's really not all that impressive. As far as noncombustion reaction goes, it's pretty big - you are breaking a relatively weak O-O bond and forming some strong O=O bonds, not to mention H-F bonds) - but I wouldn't call it scary based on just quantity of heat alone.
*It's a little unclear whether this is the case from the way it's written in the article. Even if it's 433 kcal/mole of FOOF consumed, you're still left with a heat of reaction of ~6 kcal/g of FOOF reacted, which is much less heat produced than that for combustion of alkanes. I suppose we could figure it out by looking at bond energies involved, but I'm not so eager to spend the time.
@ curious,
Yes, I'd say kinetics would be an important factor in "scariness".