Not sure that a separate key is the a great solution here. We don't want to make app menus a separately tweakable thing. How about we simply make g-s-d look out for focus-follows-mouse and do the right thing ?

Well, I think both should be done, some people may want to use the App Menu, but others may not an would like it to behave like it does on XFCE. 

My initial worry was about the app menu being in the top bar, which is why I wrote an extension to remove it. Then I read in the blog post that not only was it going to be forced but also that it was going to break the sloppy mouse focus (which is why I wrote to the list). The second issue (the focus) is actually a bug I guess, the 1st issue is an enhancement. Maybe I should create 2 bug reports?

I think that having menus in two different places isn't optimal UI design, but I won't argue with you guys if you absolutely want that, but please allow users that don't want that to be able to write extensions to change it (so that it is next to the other menus like in XFCE (see screenshot here http://developer.gnome.org/gtk3/unstable/GtkApplication.html).

I'm fine with making the setting dependent on "focus follows mouse" as Matthias mentions in comment 1, but making it a preference is out of the question. And work should really be going on to make focus-follows-mouse work, instead.

May I ask why it's out of the question? I'll give you a use case that shows where I'm coming from:

I have 2 or more screens, my main screen has the Activities menu and the App menu, but my app is in another screen, so I have to go to another screen to access the App Menu.

I guess you could put an App menu in each screen, but still, other than it being a lot more coding work than allowing us to decide to not use the app menu via a setting, it's not very good UI design IMO. I love what you have done on Gnome Shell up to now, but forcing the App menu, especially since it is possible with the current API to choose to have it along side the other menus is not the greatest thing. And I still think that even for mono-screened appliances having menus in two places isn't good, talk about confusing users.

So please, explain why you don't want to allow users to choose?

So you're trying to work around the fact that the app menu is not very well designed for multi-screen by trying to find a way to disable it. Hmm, no, work with the designers to find a better solution, and get it fixed.

I'm not interested in carrying work-arounds for designs that didn't take into account fairly common cases.

I'm trying to work around several things :

 1) It breaks the sloppy mouse focus.
 2) It's awkward/confusing to have menus in two places for an app.
 3) It's not well designed for multi screen setups.

These next reasons are personal:

 1) I personally don't like where it is situated since I don't like the Mac OS X/Unity global menu idea (I have used Mac OS X a lot for work, never got used to it).
 2) I think that the fact that it flashes all the time (since I'm moving the mouse around the image/icon & name changes) is distracting since flashing usually indicates there is something to look at (notifications).

I'm not against having a menu for app specific actions, I just think it should be in the same place as the other menus, either like in the XFCE screenshot when used by Gnome/XFCE or where it is for Mac OS X (and I guess Unity?).

My proposal is the following (since you asked :-)):

 - When an app is not in fullscreen mode, the App menu is on the regular Menu Bar like in the XFCE screenshot, the app also still has it's Title Bar
 - When an app is in fullscreen mode, the Menu and the Title bars disappear completely and it is replaced by the App menu, which has to be present on the screen that has the application (e.g. each screen has a top bar). It will have all of the application's menu items.

This has several advantages :

 - it is concise
 - it saves space in fullscreen mode
 - it fixes the sloppy focus issue
 - it fixes the awkwardness of having an application's menus in two different places
 - it fixes the multiscreen problem.

it also fixes my personal issues (which other people may also have) :
 
 - no more flashing/distractions
 - the best of both worlds

Cheers,
Gabriel

BTW, my proposal doesn't change anything when the app is in Mac OS X/Unity mode (since they use Global menus all the time), it's for Regular Gnome UIs.

Thanks for the bug report. This particular bug has already been reported into our bug tracking system, but please feel free to report any further bugs you find.

*** This bug has been marked as a duplicate of bug 671667 ***