When you press the key of a submenu, you move to that item, but not into the submenu, so the next key you touch is interpreted in the main menu and not in the submenu. So an extra right-arrow-press is nessesary.

I think it should be at least an option to go directly into the submenu. Thought I can't imagine anyone not wanting it.

I choose "do one of the above depending on a variable I have set." because user should always be able to choose a option or not...
But I guess "go the first item of the submenu." is the right way...
But I never use shortkey to navigate throught popup. Maybe I'm wrong :)

i think as smurth, the user should have an option, and i like the way it works now, staying in the selected menu.

I only just relised you could use keys to select menu items. Though it doesn't quite as I expected. I saw a problem with "go the first item of the submenu." because if you two items starting with the same character then who is to say the first one is the one you want? I expected I would be able to press the character again to go to the next item starting with the same character but it doesn't work like this.