[tomsem]

I managed to fill out the 'punch card' and got my first $3 Kindle book credit (you have to 'activate' it). Bought a $2.99 book with it, and earned another 15 points for that purchase.

In the past they have had 'Buy $20, get $5' promotions over a similar time frame to the 'punch card'. This is a little easier to achieve (though I seem to never have had a problem meeting the $20 threshold), and with the continue accumulation of points from these and other purchases, it probably means it's a little more generous. Of course we can't assume how frequently Punch Cards will show up.

I see the points earned expire when the Beta ends. But as long as you keep redeeming when you have 300 in hand, the most that can expire is 299, even if they don't let us know when Beta is over. Not much at stake, even if they don't roll over to whatever Kindle Points become after the Beta is over.