For me, on my G5 iMac:
Image previews in the Finder are "holy crap" faster.
Page rendering in Safari is "holy crap" faster.
Unfortunately, the dreaded "forward and reverse scrub can't be used in mini mode" problem in iTunes 6 is back for me. I thought 6.0.1 fixed it, but it came back. Was hoping, by some odd chance, that 10.4.3 would fix it. Nope - still there.
Image previews in the Finder are "holy crap" faster.
Page rendering in Safari is "holy crap" faster.
Unfortunately, the dreaded "forward and reverse scrub can't be used in mini mode" problem in iTunes 6 is back for me. I thought 6.0.1 fixed it, but it came back. Was hoping, by some odd chance, that 10.4.3 would fix it. Nope - still there.