Pretty compelling title, eh? And in this case, it’s all true. I just found the best Mac speed tip ever on Ars Technica.
On page 2 of that article, you find out that Apple has made some
terrific performance enhancements to the graphics rendering code of Mac
OS 10.4 (Tiger), but they are disabled by default! I guess this is
because “…It requires an ATI Radeon 9600 or NVIDIA GeForce FX or
better…”

So check your system profile, and if you’ve got the
equipment, install Apple’s Developer Tools and run this little program
called Quartz Debugger to enable all kinds of graphics acceleration
goodness. I’ve put the program in my startup list and I’ve never been
happier.

Update: OS 10.4.3 disables Quartz 2D Extreme! Apple notes this here. I don’t know why–I haven’t had any problems, but I guess some people must be finding it unstable.