I attached two files showing the issue more specific.

1) unnecessary_horizontal_scrollbar - this shows the files-in-working tree view in the log view. the untracked files are in a subdirectory of a subdirectory of a subdirectory (3 directories). None of the names requires more space than there already is in the view because the with of the view is more than enough. However there still is a horizontal scrollbar

2) toggle_scrollbar - this will only be reproducable on Mountain Lion since this is a new feature. When hovering over a scrollbar it gets bigger so it is easier to use it. Unfortunately, the unnecessary horizontal scrollbar mentioned above now gets into our way. When trying to only select the last entry (index.html in this case), the scrollbar gets bigger. This only happens if I recently scrolled. Meaning that if I wait for some time, the small scrollbar will disappear automatically and I will be able to select the last entry.