In the past the macintosh experience has been bad bad really bad. the original mac OS was designed to be friendly to end user at all costs, and as such lost a good bit of its potential power. With X, Apple has built a hard core, industrial, powerful operating system with an intuitive use user interface; however, the techies that Apple needs to win over that want to dabble with the OS can't because apple hardware is expensive.
If X was ported to intel, a legion of developers and techies (like myself) would get to play around (and use!) apple's OS.
Also, a couple of refutations to some of the bunk that has been passed along here:
"X would croak because of the vareity of hardware you have to deal with on the intel platform." - BS. Ever try installing Linux? I have not seen a computer yet that I could not get to work, whether it be a 486 or the newest Dell RAMBUS(t) machine. Now, I admit that getting vanilla linux to work and getting BSD to work are not exactly the same thing, but most of the programs that do hardware detection and driver installation are already written and would just need a recompile.
"selling X for Intel would kill the market for apple hardware and, as a result, would kill apple." - BS. Okay, take Jon Doe, a clueless computer illiterate that is buying a computer from an OEM. Mr. Doe WILL NOT be able to buy OSX with his machine. Microsoft has the OEMs tied around their little finger. Therefore, I can only see two types of ppl that would ever buy OSX on intel: 1) hard core techies (like myself) that built their own computer and are confident enough to install an operating system, and 2) former clueless users that have a tech friend and want to try it out. As long as there are legions of clueless users that buy Imacs because they go with their living rooms Apple will never go out of business.