On the other hand... I just read this on Accelerate Your Mac which augurs well:
"Hey everyone, I've been at Apple's developer conference and had a chance to install and try out After Effects on a new G5.
I ran the Night Flight file that has come to be the standard for AE benchmarking. Since I didn't want to sit there and watch it render for hours, I ran just the first 10 interlaced frames from the project's pre-set render queue...
http://www.aefreemart.com/tutorials/3DinAE/nightflight/nightflight.html
Here are my results for this test on the three computers I have available to me:
1 x 1.0 GHz G4 PowerBook 17" - ~30 minutes (3 min/frame)
2 x 2.66 GHz Pentium Xeon from Boxx - 11 min, 39 sec (1.2 min/frame)
2 x 2.0 GHz PowerMac G5 - 6 min, 1 sec (0.6 min/frame)
I ran the Xeon test on a couple different identical machines to make sure mine wasn't just running slowly, but got identical results.
Of course my Mac bias is well-documented, but I'm sure many people here can vouch for me as an honest person. If the results had gone the other way, I'd just keep my mouth shut and let someone else break the bad news.
Other observations about this test that may ultimately work in the Mac's favor:
1) The machine was not running 64-bit Panther, but only a tweaked version of 32-bit Jaguar. Likewise, AE is obviously not yet compiled to take advantage of the G5 chip in any way. Both or these situations will automatically be rectified in the future.
2) Night Flight is very CPU-intensive, but not very disk I/O intensive. I think the 1 GHz system bus and other details on the G5 will provide greater gains for typical projects that rely more heavily on I/O."