I have not bothered to look exactly how long the loading process takes, but it's definitely fast enough. Had I but known before that I charged with almost any micro-USB charging cable to the Kindle Fire war (eg the Samsung Galaxy SIII from mobile phone or the car charger our Becker-Navis), then I would have saved this purchase.
Update and depreciation: After about half a year, the two pins have somehow solved the housing (was probably glued), so plugging in the socket now a very wobbly affair is - why devaluation of 4 to 2 stars. I'm not sure if the part is still safe - yet it works.