While Apple has not proven to me that they have the world's bar-none, flat-out, no holds barred fastest computer, they sure as heck have convinced me that they have one really fast box. And that's all I wanted to hear last Monday.
Really, unless the G5 is truly a hoax, for all intents and purposes the top end boxes on both platforms seem to be on a level playing field give or take an app here and there. Fortunately for me, the stuff I use most (Photoshop, Final Cut) will probably smoke on the G5. The jury is still out for Lightwave, Illustrator, inDesign, Director, Flash, etc. Those latter apps aren't anywhere near as processor intensive, so I expect them to haul ass as well. Whether or not they technically run as fast as the top end Xeon I don't think will matter much given the nature of the aps (not so much render intensive as they are GUi intensive).
Lightwave better get their act together though as they've been really lacking on proper Mac development lately. I think I made a mistake with Lightwave, should have gone Maya.
Speed is very important. People have been saying for years that the current model of a given machine is as fast as the world needs. They have been wrong every time. Until all computers make the word "render" obsolete, and all apps open instantly (actually, they'd probably all always be open at all times many years from now) there will always be demand for more speed.
Bottom line. All current and near-future machines on the top end of either platform are REALLY fast. Let's all enjoy them.