Personally I like the new "combined" style RW/FF buttons. I didn't quite see the point of haven't 2 seperate buttons. Since you had to hold down the old RW/FF buttons anyway you might as well have them combined as you've implemented it now giving you the extra space - so i say keep those.
As for speech I can't say I use it at the moment...due to the fact that it can't hear you while playing music. If you implemented it as Predator1 has suggested above then i'd see that as a real bonus! By using a hardware button or the global NAV speech button I think people would find it much more handy! therefore making it worth-while keeping it in the global NAV.
Lastly for a configurable button I don't think it would follow the logic of the front-end. If you wish to keep it simple then keep the quick-launch style apps in the same area...being the drop-down menu. Further apps are kept in the main menu area. If you start putting too many routes to applications then things get confusing.
However!! saying that I can think of a similar function for the global NAV - a flip-between-apps function. Rather than have it quick launch an app, have it flip between the current screen and one configurable spp. You can then give that button a set icon (so maintaining performance) but configure the screen it "flips" to. If you click it takes you to GPS, click it again and it will take you back to your original screen. This would always give you one-touch access to that favourite app (I'd have it GPS so i can flip between media and GPS).
Just my thoughts!