Ugly Redactor II and how to fix it with some CSS
Here is my eye-friendly code:

/* Redactor|Fonts */
[class^="redactor-"], [id^="redactor-"] {
    font-family: inherit !important;
}

/* Redactor|Toolbar */
ul.redactor-toolbar a {
    padding: 12px 13px !important;
    height: auto !important;
}
div.redactor-dropdown, ul.redactor-dropdown {
    font-size: 13px !important;
}
a.redactor-dropdown-h3 {
    font-size: 18px !important;
}

/* Redactor|Tooltip */
span.re-button-tooltip {
    z-index: 1 !important;
    bottom: -18px !important;
    background: none !important;
    color: #333f4d !important;
    font-size: 10px !important;
}

/* Redactor|WYSIWYG-Editor */
div.redactor-layer {
    padding: 20px !important;
    font-size: 15px !important;
    line-height: 22px !important;
}
div.redactor-layer h3 {
    font-size: 20px !important;
}

/* Redactor|HTML-Editor */
div.redactor-box textarea.open {
    padding: 20px !important;
    border-top: 1px solid #e3e5e8 !important;
    border-left: none !important;
    border-right: none !important;
    border-bottom: none !important;
    background-color: #333f4d !important;
    color: #fff !important;
    font-size: 12px !important;
    line-height: 18px !important;
}


Just paste it into the Control Panel CSS plugin.