Hold on, I thought Gatekeeper would only give you verification that an app is secure, and you would otherwise still be free to install any app you want. Is Apple really restricting you to install only app store and Gatekeeper verified apps?
There is a simple preference you can use to disable Gatekeeper entirely.
The default setting is to require that the app either come from the App Store or be signed by the developer (app signing is available through your ADC account)
Disabling it is as simple as changing one setting.
EDIT: If I sound a little frustrated, it's because people keep posting questions like these, and it's getting to the point that it appears rhetorical. Take 3 minutes and read just about any article that covers Gatekeeper and the answers to these questions become abundantly clear.
The repetition of this question, stated in this specific manner, is causing a deluge of rumors and misinformation. I've already been told by two non-tech people, "I heard Apple is making everyone use the App Store in the next version of OS X."
If that weren’t enough, OS X Mountain Lion is introducing Gatekeeper, which will, by default, limit the apps you can install to apps from the OS X store or verified Apple developers.
On the very first page of Google search results for "os x gatekeeper" is the official Apple page, with the screenshot of the preference panel:
http://www.apple.com/macosx/mountain-lion/security.html
That's 30 seconds of looking for anyone capable of typing two terms in to Google.
The day that OS X will require jailbreaking to customize is the day I give up completely on Apple.