This is a great resource for someone who can't find the critical & fumble card decks for Pathfinder, or just prefers a dice-rolling mechanic over card draws.
As someone who actually knows the person who wrote the Dragon Magazine article the authors cited, they are a worthy successor to that article.
However, if there is any real lack to these charts, it is one shared with Carl's, in that they are designed with melee weapons in mind. Blunt weapon criticals work in a pinch for weaponless combat, but the weapon fumbles bring on an uncomfortably high level of broken bones (I had one monk PC break both hands in a single melee from fumbles, and was reduced to kick attacks, on the FIRST ENCOUNTER we used these charts), given how monks are much more popular and playable in PF & 3.x. And there are so many things that can go wrong with missiles that have no comparison in melee, and melee accidents that can't happen in missile fire.
I wouldn't mind it if somewhere down the road, the authors would expand it to have a separate critical charts for missile weapons & weaponless combat, and develop separate fumble charts for each weapon type, missiles, unarmed and animal attackers. What works as a fumble for a longspear doesn't necessarily work for an arrow, thrown dart or bite attack, nor does a fumble chart written for a sword really work when it's a monster fumbling with a claw attack. The current table that clumps all fumbles together still results in the occasional headscratch.
I would also suggest that the authors explore using 2 columns per page on the charts that run over one page, to see if they can get them to fit on a single page.