So I see that Plants vs Zombies, the version I already bought on the amazon app store, is not the version that shows up now. They apparently went and made a "kindle fire" version, that supposedly has higher resolution. And they want you to buy it all over again. Never mind the fact that I'm like halfway through the adventure and want to continue from where I was.
On one hand I'm glad to see apps taking advantage of greater screen resolution and real estate. But on the other hand I'm thinking this should be done as an update to the existing product. I actually went ahead and bought it to see if there was anything different, any new play modes, levels, etc. As far as I can tell nothing. I probably wouldn't have noticed the increased resolution if I hadn't been looking for it (I had previously played on a 4.5" infuse at 800x600).
FWIW I was able to load the apk from my existing pvz just fine as well.