1. Returns are short but possible.
Any app purchased from the Android Market can be returned within 24 hours from the time of purchase.
2. Reinstalls are free.
The Android Market allows users to reinstall purchased apps an unlimited number of times.
3. Upgrades arent done through the Market.
The official policy states that any upgrades must be obtained directly from the Developer as the Market has no upgrade functionality.
4. Sexually Explicit Material is a no go.
The market does not permit nudity, sexually explicit material, or apps that drive traffic to commercial pornography sites.
5. Youre on your own.
Google makes it clear that they bear no responsibility in billing disputes related to app purchases.