How to deal with INSTALL_PARSE_FAILED_INCONSISTENT_CERTIFICATES without uninstall?

It means the new copy of your application (on your development machine) was signed with a different signing key than the old copy of your application (installed on the device/emulator). For example, if this is a device, you might have put the old copy on from a different development machine (e.g., some other developer's machine). Or, the old one is signed with your production key and the new one is signed with your debug key.

I ran into this while testing on a new Xoom. I had previously installed my app from the Marketplace. Later while trying to test a new version of the app I ran into this error.

I fixed it by removing the app that was installed via Marketplace (just hold and drag to the trash). Thereafter I was able to deploy my development version without any issue.

This happened to me when another developer on the team built our app on the hardware device I was trying to deploy to. Uninstalling the app from hardware fixed my problem.