There is a little hysteria going on in this thread. Notarization is not some slippery-slope way to a walled garden. It is simply an extra step after code signing. It seems some nefarious apps have gotten into the wild, that were signed with ostensibly valid certificates. Apple has revoked these certificates, upon discovery. With notarization, a developer's signed installer is sent to Apple; they audit the code for security, and "staple" the package with their virtual "notary stamp." This is what the developer then distributes.
I'm a developer, and I've already notarized my Mac products. It just takes me a few minutes. Notarization is only for applications distributed outside the MAS, as it's somewhat redundant otherwise. The user experience should be not too different from now. As far as I know (maybe someone else does "know"), the existing procedures whereby a user can choose to install an unsigned application are unaffected.