This Stepwise article describes one developers use of OpenStep/Cocoa in his Playstation game development:
To many who have had the pleasure of working with it, Cocoa is the greatest thing since sliced bread. It's been variously described as 95% of the utopian programming environment you've always dreamed of, the way application development should be done, and a decade ahead of its time (even today, more than a decade after its birth as NeXTSTEP). Getting to know Cocoa makes developing on any other platform seem unnecessarily painful and cumbersome by comparison.
To many who have had the pleasure of working with it, Cocoa is the greatest thing since sliced bread. It's been variously described as 95% of the utopian programming environment you've always dreamed of, the way application development should be done, and a decade ahead of its time (even today, more than a decade after its birth as NeXTSTEP). Getting to know Cocoa makes developing on any other platform seem unnecessarily painful and cumbersome by comparison.