I use Cocoa to write extensions to a scripting language (Tcl). It is a different beast; memory management is a bit tricky, as well as figuring out how to call into Cocoa from Tcl's C API. Finally, it's a bit hard to get my head around writing 200 lines of Objective-C that boils down to two Tcl commands. Still, I'm glad I'm learning it. Also, for what it's worth, it's easier to call into Cocoa than Carbon...