Session Menu's icon has been redesigned in Oneiric Ocelot
There were some rumors concerning a new icon theme in Ubuntu 11.10, but, now, it is almost certain that the new icon theme will land 100% in Oneiric +1.
Nevertheless, new icons are still landing in Oneiric.
A previous update put a colored "Computer" icon on the Unity panel that was breaking its consistency.
Just now, another update fixed this issues, and, Oneiric features now a new redesigned Session Menu monochrome icon.
You can also admire this new icon on LightDM login screen's "special" indicators, too (they have limited functions, so, you can't anymore, for instance, start Banshee, Time & Date Settings, etc).