I am deciding whether to use or not XIB files in my solution. In previous versions of monotouch and Interface Builder, i chose to go xib-less but now with xcode 4 integration, IB seems more user friendly, and the fact that all the UIViewController/UIView class templates in Monotouch create a xib file. Also, most of the new monotouch tutorials and examples suggest that we use IB.
Can someone point me in the right direction ? Are there any situations in which is best not to use XIB files ?
XIB files can still be slow to load if you put too much content in them that needs to be loaded at startup. I generally avoid XIB files because they do not do much in terms of improving my developer experience.
That said, with iOS 5, they introduced Storyboards which allow you to design your application flow from a single place and it will then break down the storyboards into XIB files that have been tuned to only load what you need per screen.
Storyboards in my opinion do bring significant value that you did not really get with XIB files and are worth using.