I wanted a superfish menu in the menubar and the default styling is pretty awful, so I added the following to the Custom CSS extension.
This is for horizontal menu only.

/* Menu bar / superfish */
#menu-bar {
  padding-top: 5px;
  height: 24px;
}
.sf-style-none a  {
  padding: 4px 8px 8px 8px;
  margin: 0px 0px 0px 0px;
}
.sf-style-none a.sf-with-ul {
  padding-right: 2.25em;
}
.sf-style-none.rtl a.sf-with-ul {
  padding-left: 2.25em;
  padding-right: 1em;
}
.sf-style-none li {
  margin: 0 0 0 0;
  padding: 0;
  background: #BEBEBE;
}
/* undo default shadow */
.sf-menu.sf-horizontal.sf-shadow ul {
  background: none;
  padding: 0 0 0 0 !important;
}
/* redo shadow with box-shadow */
.sf-menu.sf-horizontal.sf-shadow ul {
  -moz-box-shadow:5px 5px 8px #666;
  -webkit-box-shadow:5px 5px 8px #666;
  box-shadow:5px 5px 8px #666;
}
/* fix arrow position */
.sf-horizontal .sf-sub-indicator {
  top: 6px;
}
/* mouseover */
.sf-style-none li:hover,
.sf-style-none li.sfHover,
.sf-style-none a:focus,
.sf-style-none a:hover,
.sf-style-none a:active {
  outline: 0;
  background: #CECECE;
}
/* dropdown position */
.sf-style-none li:hover ul,
.sf-style-none li.sfHover ul {
  top: 28px;
}
.sf-style-none li li:hover ul,
.sf-style-none li li.sfHover ul,
.sf-style-none li.active-trail ul {
  left: 0;
  top: 0;
}
/* active page */
.sf-style-none a:active, .sf-style-none a.active {
  color: #004000;
  background: #C0C0C0;
}

Hope this helps someone.