According to some of the remarks and links here:

http://forums.macnn.com/showthread.php?t=251882

I am lead to believe Tiger will make my 1.5 Ghz 17" Powerbook run like a 1.9 Ghz 17"...
One sure way to proove it is to see if HALO runs any better; It stutters a lot on 10.3 without patches (which are supposed to smooth it out), which I never downloaded cause the patches prevent you from playing without the CD. We'll see.