All apps that you get from the Amazon App Store will be listed and waiting for download to the devices you assign to your account. So far I have about 6 apps that can be downloaded and installed both my phones and my Xoom. My CC info was already on file and set up with amazon because i am a Prime member so no big deal for me there.
Also, keep in mind that if you download an app from Amazon and it replaces the same app from Android Market, the Android Market will remove it from the list of your apps it keeps and it's updates will come from Amazon now.

