I would love to be able to hide the top server tabs bar on my single-server setup. Lots of wasted space when I don't have any other servers. I like to have the window fairly small, sort of old-school instant-messaging style, and when I do, 5% of the height of the window is taken up by the tabs bar (yes, I'm that kind of person where I measured the height of my window in pixels and the height of the tabs bar using GIMP).

Even if I were connected to other servers, I could switch servers using a keyboard shortcut (Ctrl+Number, I believe) and wouldn't need that huge bar on the top to see the servers I'm connected to. I guess the only benefit to having the bar there with multiple servers is the notifications indicator and the 3-dot menu for the Menu bar. Still, these could be moved elsewhere that doesn't take up vertical space.

Running on Arch Linux with Gnome.