Maximum fee percentage
From the README:

> To be fast (confirmation within seconds), Kasisto will accept unconfirmed transactions. Combined with the current transaction fees of around $0.25, the targeted payment amounts should be between $10 and $100. I don't know how likely it is that a transaction will not get mined, so every seller will have to find their own pain barrier. Similarly, buyers will have to find their own personal lower limit in regards to current transaction fees.

Regardless of current fees, I'd be interesting if anyone could comment on their personal maximum fee they're willing to pay, as a percentage of total amount being paid.