Comment 53 for bug 12040

For me, the delay is unappreciated, less than a sec (~ 0.5s). I think the next will improve the behavior:

I've edit (create) ~/.gtkrc-2.0, adding

             gtk-menu-popup-delay = 0

I'm sure that there is no problem when you have "Menu Bar" loaded into the panel too, so you can put the "Main Menu" next to the "Menu Bar" and you will see Ubuntu logo twice. But if you want to have the "Main Menu" alone (like i want) the problem will persist.

So the problem is not gnome-panel neither gnome-menu-bar, it's gnome-main-menu.

I suppose that if you have a theme with large icons or similar, the time to load them will be bigger.

I hope this will be for help.
Sorry for my English.