Shortcut to switch between Today and Notifications in Yosemite
Applescript:

tell application "System Events" to tell process "SystemUIServer"
    click menu bar item "Notification Center" of menu bar 2
end tell

tell application "System Events" to tell process "NotificationCenter"
    click radio button "Today" of radio group 1 of window "NotificationTableWindow"
end tell


Depend on what an user needs, whether it's to switch when the menu is pulled out, or to simply access Today or Notifications on demand, one can modify the above code and bind it/them to keyboard shortcuts.