Amazon’s entry into app store sales today promises to deliver what Google hasn’t been able to so far — real paid downloads and in-app payments for Android developers.

The company, with millions of credit cards on file and 1-click ordering, might be able to convince consumers to pay where Google Checkout has so far had a complicated user experience. Although to be fair, Google is in the process of overhauling its payments solutions and will launch in-app payments to consumers by next quarter.

Because of Android’s open nature, expect a tight race between Amazon, Verizon and others to be the next best marketplace alongside Google’s officially sanctioned one. At the very least, Amazon’s debut should pressure Google to fix up many of its marketplace’s existing problems like discovery, opaque rankings and payments.

While Amazon’s app store doesn’t come pre-installed on Android phones, the Seattle-based company is trying to compensate and attract consumers in a number of ways:

1) Amazon is allowing customers to “test drive” apps, or use them on a simulated Android phone within the web browser before they buy. This should help prevent the returns problem, where consumers install an app only to return it minutes later. It used be a more severe problem when Android Marketplace’s returns window was 24 hours; it’s now 15 minutes.

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