I don't know that that's been the case on OSX though — since 10.0 the story has consistently been that each release is as fast or faster, albeit more memory hun

I don't know that that's been the case on OSX though — since 10.0 the story has consistently been that each release is as fast or faster, albeit more memory hungry. I'm sure I'm missing one but I can't remember any OSX release being associated with performance complaints.