Is it possible to design NSTableView cells using Interface Builder? I know this is actually possible if your project is for iOS but somehow IB does not render the cell container if its for Mac OS X.
Im not sure if Amy gave that answer when this couldn't be done before, but this can be done quite easily on interface builder.
It can be done using view-based table view cells (instead of cell based) shown in the apple docs. There's is even a decent example you can download from the reference site.