My iOS app, iOS6 and iPhone5 compatible, was just reject due to these vague reasons:
10.6: Apple and our customers place a high value on simple, refined, creative, well thought through interfaces. They take more work but are worth it. Apple sets a high bar. If your user interface is complex or less than very good it may be rejected
0.6
We found the following issues with the user interface of your app:
Does not use expected iOS gestures.
Did not integrate with iOS features.
Did not include iOS features. For example, it would be appropriate to use native iOS buttons and iOS features other than just web views, Push Notifications, or sharing.
These examples identify types of issues discovered in your app but may not represent all such issues. It would be appropriate to thoroughly evaluate your app to address these types of issues.
Resources for learning how to improve your app:
Watch the video The Ingredients of Great Apps to understand the basics of great apps
Watch the video iPhone and iPad User Interface Design for practical design tips
Read the iOS Human Interface Guidelines and double check that your app's user interface adheres to these valuable guidelines.
Read the App Design Basics section of the iOS App Programming Guide.
Watch the iOS Development Videos to learn about programming and design tips.If you feel we didn't understand the features of your app, or that we missed key functionality, and your app was incorrectly rejected, you may appeal to the App Review Board.
Can anyone please give me some direction where should I look? apparently I can't see anything specific where too look at in my code or UI.
Their key suggestion was "Read the iOS Human Interface Guidelines and double check that your app's user interface adheres to these valuable guidelines." You can find these here:
From their vague description, it sounds like your app may not include some of the default expected UI behaviors and gestures. I'd read the guidelines to verify what those are then make sure they are implemented in your app.