[hammerandtongs]

This in my userChrome.css works very well for me.

  #TabsToolbar {
        visibility: collapse !important;
      }

There are no real glitches or problems but can't imagine living in Firefox without TreeStyleTab in general over minor issues.

[rbaud]

I've been using the following in Win 8.1:

  /* to hide the native top tabs */
  #TabsToolbar * {
      visibility: collapse;
  }
  /* to give the top toolbar a bit of height so the window controls don't dangle off to the right */
  #TabsToolbar:before {
    content: '';
    display: block;
    width: 100%;
    height: 20px;
  }

  /* to hide the sidebar header */
  #sidebar-header {
      visibility: collapse;
  }

[wlesieutre]

Have you tried the built-in titlebar setting in Customize? There's an option at the bottom to turn on the regular system titlebar so that it displays as a normal window.

[rbaud]

I have not. Thanks for the tip! I'll give it a whirl when I have some time.

[themechanic]

For those using OSX, increase the height to 40px

[lousken]

@namespace url("http://www.mozilla.org/keymaster/gatekeeper/there.is.only.xu...");

#TabsToolbar {visibility: collapse;}

#titlebar {margin:0px !important; display:none}

#sidebar-header {visibility: collapse;}

#nav-bar-customization-target {margin-top:10px;}

I use this with titlebar disabled