The touch-ups to Ubuntu's default look in Karmic are a bit short of the complete overhaul that Mark Shuttleworth has alluded to since the time of Hardy's release. But they represent much more than the negligible aesthetic changes that have marked other recent releases.
System themeAlthough the rusty-orange color scheme that Ubuntu users have known and loved (or not) for years remains prevalent in Karmic's default wallpaper, Ubuntu 9.10's window-decorator theme features a dark-brown tone.
Besides the color change, the window decorations haven't changed much since previous releases. This is still the "Human" theme, just in a different color.
IconsThe second major aesthetic update in Karmic is a (with few exceptions) totally new set of default icons. Here are some examples:
The applets in the system tray have also received a makeover:
Nor have Nautilus icons been neglected:
In my opinion, at least, the new icons, which are more detailed and three-dimensional, are a refreshing update to the simplistic artwork that has predominated in previous Ubuntu releases.
A total overhaul of the Ubuntu look will have to wait for future releases. But for the time being, the touch-ups to Karmic should help placate users who worry that Ubuntu's default look is ugly and outdated.