For per-user installation:

Current implementation, deliberately as simple as possible: /opt/click.ubuntu.com/.click/users/$user/$app_id is a link to the version of $app_id installed for $user.

As an example, /opt/click.ubuntu.com/.click/users/cjwatson/com.ubuntu.apps.camera -> /opt/click.ubuntu.com/com.ubuntu.apps.camera/2.9.1daily13.06.13

A .desktop file will be installed at ~/$([[../ApplicationId|application_id]]).desktop.