How does ICS deal with Menus on devices with physical buttons? ICS removed the need for the Menu key with always visible action bars, but also has support for phones which come with hard keys. Traditionally the menu button brought up a context menu.

I've got a device with hard keys, if I upgrade to ICS will the Action bar always be visible, standard ICS style, or will it be hidden under the Menu key? What will the menu key do in ICS?
The menu button will display the action overflow menu, and the action overflow "soft" button should not appear on the Action Bar. The Action Bar itself, however, will still be visible as it normally would (provided the app implements it, of course). The Android Design guidelines for the Action Bar state (emphasis mine):


  Action overflow
  
  The action overflow in the action bar provides access to your app's
  less frequently used actions. The overflow icon only appears on phones
  that have no menu hardware keys. Phones with menu keys display the
  action overflow when the user presses the key.


For the sake of clarity, the "action overflow button" is the little three dots icon shown at the far right here: