Before upgrading to iOS 6, I can just watch iTunes U videos with all other videos from my Mac's iTunes library in the Videos app on my iPad via Home Sharing. However, the first time I open the Videos app on iOS 6, I was told I should watch iTunes U contents in the iTunes U app. But I see no videos in the iTunes U app.
I could resolve the issue by removing the Podcasts and iTunes U apps from the iPad. Afterwards the shared items are visible in the Videos app.