I would be nice to have an option to publish a ClickOnce application to a secondary location, so that updates can be tested before being published to the primary install point.
This secondary install point could also allow for the application to be renamed, so that they appear to be separate applications within the user's list of installed software (for easy removal after testing.)
The purpose of this request is so that major changes to an application can be thoroughly tested in the user environment before being published to the main application installation site.
Currently, to achieve this affect you must rename the application, change the Publish Location and (for sanity checking) modify the version number. After publishing the test application, the project must have the original properties re-assigned.
The above steps are easy to follow, however they can be error prone. Having a secondary, or multiple install points could make the process of user or beta testing much simpler.