1) the up/down arrows don't scroll in small steps, but instead jump to the beginning/end of the list.
2) the scrollbar handle does not center on the vertical position of the mouse pointer when grabbed, but is below it instead.
I cannot reproduce this. They work just fine for me.
WHen click is set to "Jump to here" I can repro.
Created attachment 25049 [details]
Fixed in r38312.