They're panels. There's one task bar (window list) on the bottom panel by default. And you can get rid of them now if you want. I'm reading comments like above mentioning how Linux Mint's look is aesthetically pleasing. Really? It's almost all GNOME. Why discuss a whole change of distro to get a different theme/look? Just change the theme.
It's not even like you're downloading third party apps or doing registry tweaks/resource hacks on Windows 10 years ago. Context menu→"Delete this panel". It's less of a hassle than managing your desktop icons. It's just like making sure Firefox's "Always show the tab bar" preference is set to the value you want it to be.
More broadly, it seems like any level of hullaballoo about Ubuntu's default theme is too much. Who actually sticks with the default theme?
I usually stick with the default theme, except for reconfiguring the panels. Why change the default theme? Last time changing themes excited me was when I had an Amiga 500.
There's hardly excitement from me. My choices are mostly functional; I think skinning culture is kind of silly (e.g., especially so with the hype about Mozilla Personas). There are things that I could do to make things look nice or gimmicky, but I'm definitely happy to do without for functional gains, and I do.
Is it easy to exchange themes? I might be bothered to theme if there is an easy way to set the theme on every computer I use. I suppose some productivity enhancements are possible, I just never took the time.
System → Preferences → Appearance to tweak installed themes and create new ones. There's a link there to get more, but there's also http://gnome-look.org. The ones from gnome.org are easier to install, because they send the "Content-Type: application/x-gnome-theme-package"
header, while gnome-look.org just does plain ol' gzipped tarballs. (Actually gzip vs. bzip vs. raw tarballs might be up to the uploader, I don't know.) You can also save the theme packages, and drag and drop them in the appearance preferences window.
Also, terminology. I think "theme" refers to a packaged deal, which can include window borders, gtk controls, icons, colors, desktop background, maybe more. So the frustrating thing you might find is that you see a theme you like, but it changes your colors and gtk controls, and uses an incomplete icon set, when really all you wanted was the window borders. If you install it, you can do something like revert back to the default Ubuntu theme, click "Customize", and change the window border to the one installed by the theme. This is is probably easier than trying to customize the new theme itself, especially since if you're used to the Ubuntu theme, you'll probably find that your desired look has more in common with it than the new one you just downloaded.
My enhancements are pretty low key. I mute the colors, scale down the font size to 9 to make more use of screen space, and use the SlicknesS window border, which has a smaller footprint than the Human window border.
Something else that's mildly frustrating is that the window borders' colors have almost (completely?) nothing to do with the color scheme. If you think, "Oh I like this, but I'm going to get rid of the insane colors.", you're probably out of luck.
