Defaulting to deleting the zip of the previous install makes perfect since, but deleting the installation is **not** ok, since that could be your previous production install which will have critical logs, etc. I know that this is currently called "qa-upgrade" but we're aiming for a tool that can be used to more generally update, and you definitely shouldn't assume you can just blow away that directory. In some situations, the data may even be stored under it!