Perhaps you're missing something. XIBs are arguably among the most powerful features of Cocoa. I built an app with a really complex, dynamic layout using them (look up "Panna" in the App Store). Working with an evolving design and changing team, with layout elements often changing and getting tweaked in tiny ways... Well, if I did the entire layout in code, I would have needed a full-time developer just for the ongoing GUI changes. I agree that dynamic layout support was weak pre-constraints, but it was still a much better development experience, and now you can do really complicated things without any code at all.
If you're just talking about some buttons in a toolbar, go nuts, but otherwise it's worth the time investment to learn.