Looks really good! My only suggestion might be to add a bit of padding under the Main Menu alternate text to match the top padding as I have done below.
s5_flex_menu.css - line 153
#s5_nav li .s5_level1_span1 {
background: none repeat scroll 0 0 rgba(0, 0, 0, 0);
display: block;
padding: 8px 12px;
}