You are all 100% correct that a good local GUI shell could be written for Linux. In fact thats why I brought up OSX because IMO thats exactly what Apple did ontop of FreeBSD. However the Linux community seems entirely X centric so i have my doubts it will happen there. Still I could be wrong.
Currently you are right, although (as already said several times) the current license problems of XFree86 will lead to changes. Y-Windows is the only promising approach that I know of. There is also Fresco and some windowing systems for embedded devices. Fresco (http://www.fresco.org
) uses CORBA for language independance, but it doesn't look like it will be established as a standard. It's important to take the best of all worlds and userinterface consistency is certainly a strength of Mac OS X. Server-side widgets are definitely needed to get there.
And yes when I referred to it being "too expensive" that was indeed short hand for its client/server nature that requires many more layers of communication and processing then necessary for a local GUI. Its an expense a desktop system doesnt need to be paying.
I quoted something in this thread, which basically says: Not the client/server concept is slow, but the implementation X has for it. ("Slow" means a high latency. Throughput of X is good.)