Having recently introduced myself to Cocoa through
Cocoa Programming for Mac OS X by Aaron Hillegass, I would have to say that Cocoa is quite fun to program for. Specifically, Apple's Interface Builder allows you to quickly build up a GUI without writing a single piece of code. A lot of common tasks require next to no code at all. For instance, adding tabular data requires only that you create your model in XCode and perform all other tasks in Interface Builder. Within seconds your application can have a table with movable, sortable, editable columns. The only code you have to worry about is your model. Of course, should you want to do something more complicated with tables you can.
Tabular data is just one example, but there are many other ways in which programming for Cocoa is quite easy. Copy and paste using multiple types is a snap, and drag and drop is just a slight extension on top of that, accomplished in minutes. Can Windows' Visual environment say the same? Friends of mine who have implemented drag and drop on Windows spent days doing so, and it still didn't work quite right. The broken nature of drag and drop in many Windows apps is the result.
Since Mac OS X uses PDF as its native format, creating PDF versions of your data requires only a few lines of code. Similarly, Cocoa provides support for many data formats such as RTF, PNG and TIFF so saving and reading images is a no-brainer.
