If I had one quibble-- and this is a very minor thing, because it's more on me than the rules-- it would be that rolling a 20 always elicits a groan from me. It's supposed to be the best roll, but I don't get excited, instead I get sad, because I know my next action will fail, no matter what it is. That seems counterintuitive, to me.
I have been trying to make 20's even more significant, really trying to milk the specialness beyond my first ideas, but I've also been considering a house rule that, when you roll a 20, your new Kismet resets at 10.