I don't agree at all: I think that apps should be installed as admin and auto-updated. I don't follow any of your arguments that installing things as non-admin are more secure.
It's more secure because you don't have to delegate admin access to random people to install the software. Any of these "RAT kits", I guarantee you, requires admin access to the system at one point or another, be it during the install, by explicitly asking for admin password, or implicitly by using the fact that most users are logged in as admin.
