Could you be more specific in regards to the problems your having with iTunes U?
Honestly a good rule of thumb is that Apple's system apps (ie, the apps that ship with the phone, so Settings, Safari, Calculator, Calendar, etc) are very well optimized and work very well with the phone, mostly because Forrester and now Ive worked very very closely with the hardware teams to make sure the apps work as near to perfect as possible (which of course doesn't happen, but it gets darn close).
However, Apple's secondary apps that you can download from the App Store (iTunes U, Podcasts, Apple Store, the iWork/iLife suite) are far far behind in optimization and design quality as compared to the system apps. There's obviously some sort of disconnect between the various software teams housed within Apple and the main UI and hardware team that is responsible for the phones. My recommendation is: if there's a third party app that does what you want, download that instead of an Apple one.
