I've happily adhered to the AppStore requirements in the past. Accepting it as a necessary requirement for access to a nice marketing and distribution channel for independent apps. The rub now is here "Apple wants to help you steer clear of malware EVEN WHEN YOU DOWNLOAD APPLICATIONS FROM PLACES OTHER THAN THE MAC APP STORE". (source: http://www.apple.com/macosx/mountain-lion/security.html)
I would image the user experience would be similar to that of a browser warning: "WARNING: this site may harm your computer". No one clicks through those warnings unless they are illiterate or stupid. However, in the case of OS X, this type of warning could potentially create a barrier of entry for completely legitimate software composed by an independent developer who choose not to use the AppStore distribution method.
I admit it. iOS was slippery slop and we are sliding. I'm not sure the quote, but here is a crappy paraphrase: "How long will they strip away our freedoms? As long as we let them."