It fixes a bug where items would go missing in finder windows with alot of files in them. My downloads folder currently has over 2000 items in it (I haven't cleaned it out in forever) and under 10.0.2 the finder would only show anywhere from 700 - 1400 of them. It seemed to go alphabetically and usually cut off at around the letter M.
Also fixed, but not announced, is a clipping bug that I reported - under 10.0.2 when you dragged some text onto a closed folder in the Finder, the clipping file would be positioned off the bottom of the window, under 10.0.3 it appears correctly. OSX uses the lower left as its drawing origin, OS9 uses the upper left.