GP 2.0: pull down menu on navigation disappears too quickly on mouse out?

Can you link me to your site so I can see the issue?

removed

You need to remove this from your custom CSS:

.main-navigation ul ul {
    margin-top: 10px;
}

Hmm, It was working properly when v1.x
I would like to keep margin to match edge of header and menu.

The menu now uses CSS instead of JS for performance reasons.

It was working before because the JS was adding a bit of a delay before the sub-menu closed. If you slowly moved your mouse down, this same issue would have happened.

You can try offsetting that gap by adding this (in addition to your CSS):

#menu-top > li {
    padding-bottom: 10px;
}

Thank you.
Solved.

You're welcome :)