I've never used OSX, but I would guess from screenshots that it didn't do dynamic layered gaussian blur of large screen regions in realtime, which would've been too much for the hardware of the year 2000.
Also, those scrollbars were quite impressive for their time.
I've never used OSX, but I would guess from screenshots that it didn't do dynamic layered gaussian blur of large screen regions in realtime, which would've been too much for the hardware of the year 2000.