I noticed that the App Store (at least on my iPhone 4 running iOS 6.0.1) reverted back to the old layout. I also tried to see if I could hide previous purchases and I could. Anyone else getting this??
So it *was* some weird glitch that also affected my iTunes Store app, and it drove me crazy. But I figured out a way to fix it in case it happens to others. Simply sign out of our Apple ID account (Settings>iTunes & App Stores) and sign back in!