There are many small things that I like about OS X that never seem to make it into the graphical re-skins. Things like coherence of applications "feel", as well as more tangible features such as consistent and global keyboard shortcuts in every app (ie. Cmd + , for preferences). The visual polish of OS X is the least important thing that makes it usable.
Do you think a project like Nextspace could be the foundation for a Linux desktop experience more on par with the consistency of OS X?