Stubborn SOB that I am, I tried to create a macro that I could spam using one key that would allow me to dismount and stealth rapidly, without having to rely upon an addon. And succeeded!
/script i=1; while(UnitBuff("player",i)~=nil) do if(strfind(UnitBuff("player",i),"Mount")~=nil)
then UseAction(26) end;i=i+1;end; CastSpellByName("Stealth")
I put a line break into the code snippet to make it fit on the screen in this forum post; remove it to make the macro all one line if you copypaste it.
Substitute 26 with the number of the button to which you'll bind whatever mount you prefer, and "Mount" with a keyword appropriate for the buff that your character receives when mounted. To get the name of the buff, you can try:
/script i=1; while UnitBuff("player",i)~=nil do DEFAULT_CHAT_FRAME:AddMessage(UnitBuff("player",i)); i=i+1; end
