The thing about X is the protability. The fact that *IF* you have a compliant X-server running your display... it just works.
Gene, you could probably run you stuff on a Cygwin/Xfree86 Display.
X just works. Yes, it is all just works.
The only thing you have to worry about is slow links (network links)
To combat those, you send widgets that the X-Server keeps hanging around "caching" them.
People from the dark side don't want to admit that X is better at most things.