It's important to distinguish between NIBs (or XIBs, if you prefer) and storyboards.
NIBs can be used in even extremely complex and large applications to make tasks easier. For example, iPhoto on iPad uses NIBs to load in UI interface assets as it's more convenient than doing it in code - and this is an app with a large development team and a significant codebase (there's an interesting WWDC 2012 video available on iPhoto's iOS architecture, which is where I got this piece of trivia from).
One of the problems with storyboards - versus NIBs - is that it can become difficult to work at scale. Not scale in terms of team members (although that can be a problem), but scale in terms of the size of your app's UI. A iPad app with a a dozen different screens of content can become very hard to navigate.
Where storyboards are useful is allowing those new to the platform to get up to speed on concepts such as custom table view cells, collection views, auto layout and the like without having to get bogged down in the large amount of code this would normally require. They're definitely not for everyone.
Sadly, NIBs have a bit of a bad reputation with some developers. I suspect this is mainly for historical reasons - as of Xcode 5 the XML schema has been significantly simplified making code review and source control much easier, and NIBs have significant advantages for newer technologies such as auto layout.
One way ive found to handle scale in storyb
oards (in both terms of scale) is RBStoryboardLink which allows you to separate an app into multiple storyboards and use placeholders to jump into another one.
NIBs can be used in even extremely complex and large applications to make tasks easier. For example, iPhoto on iPad uses NIBs to load in UI interface assets as it's more convenient than doing it in code - and this is an app with a large development team and a significant codebase (there's an interesting WWDC 2012 video available on iPhoto's iOS architecture, which is where I got this piece of trivia from).
One of the problems with storyboards - versus NIBs - is that it can become difficult to work at scale. Not scale in terms of team members (although that can be a problem), but scale in terms of the size of your app's UI. A iPad app with a a dozen different screens of content can become very hard to navigate.
Where storyboards are useful is allowing those new to the platform to get up to speed on concepts such as custom table view cells, collection views, auto layout and the like without having to get bogged down in the large amount of code this would normally require. They're definitely not for everyone.
Sadly, NIBs have a bit of a bad reputation with some developers. I suspect this is mainly for historical reasons - as of Xcode 5 the XML schema has been significantly simplified making code review and source control much easier, and NIBs have significant advantages for newer technologies such as auto layout.