One of the reasons many Gnome users were frustrated with default Gnome 3 Shell was the lack of power off button by default. All you got when clicking of the user menu at top right was a suspend option. You might have to waste some moments to search Google and learn to use the Alt key to get Power Off.
But from Gnome 3.6, you will not need to do this as power off option will be present by default in the user menu. We have been closely following Gnome development and here are some of the latest screenshots of the new design. This is the screenshot of recently designed user menu by Allan Day. For the single user mode, the options 'Switch User' or 'Logout' doesn't make any sense, so they have been omitted.
If you have multiple users in your PC, you will get this image containing the previously omitted options.
And if you run multiple desktop environments, you will get a 'Switch Session' option along with other regular options:
The suspend option has been let off, and you can suspend your PC by simply let it go to sleep. Also, talks are on in introducing both Power Off and Suspend options in the menu for keyboard-less devices.
Seems like Gnome developers are paying close attention to what users need and are enhancing the user experience. Gnome 3.6 seems to be an awesome release.