i've put the iOS 6 GM on my iPhone 4 (not 4S), and the 'rate it' buttons in my own app and others no longer do their thing. instead it opens the app store w/ "cannot connect to itunes store". regular app-links from safari work fine.
i'm using links of this form:
itms-apps://ax.itunes.apple.com/WebObjects/MZStore.woa/wa/viewContentsUserReviews?type=Purple+Software&id=<APP_ID>
for example, from safari on iOS 5.1, the link on this page works fine: http://elenzil.com/scratch/appstore
but the same test w/ iOS 6 yields the problem i describe.
.. i have to say the App Store in general seems a bit buggy in the iOS 6 GM. i'm seeing issues scrolling through the list of search results, mainly.