I decided not to use Core Data (Tiger only technology). A minimum target system is 10.3 "Panther", because bindings are really useful (16%+49% are Panther and Tiger users, according to
this). Also, I stopped copying the design from the XCode samples and made a new, much simpler architecture from scratch for managing views, floating palletes, and so on. When I first saw the samples I thought "this is the way" that applications need to be designed, however I'm sure it's not.
The new design pattern uses NIBs and bindings extensively, instantiating classes directly from the NIB and using MVC for functionality. Still have to figure how to perform something like UpdateAllViews().