See previous post -- too much to learn. Among others, Aaron Hillegass has praised WebObjects. He has held it up as a standard against which to measure recent changes to Cocoa (and its Controller layer), and has sometimes found the latter lacking.
Haven't yet had a chance to do much with CoreData and the modeling tools in XCode 2.0. Now XCode 2.1 may help me understand what the fuss was all about.