I never understood why Apple assigned command-space to language switcher. For most people it will conflict with Spotlight. I changed it to Shift-Command-Space.
But I actually like the HUD, it could be a little "fancier", or graphically pleasing. But in general it's a good idea. You don't need the menu bar icon. But even if you use the menu bar icon, you don't have to move your eyes up from whatever you're doing to see which language you're on.
But I guess it's all a matter of habit.

Just FYI, the Cmd-Space shortcut for keyboard layout switching was used as far back as System 7 (maybe earlier, but I didn't use multiple scripts before then), so it long predates Spotlight.

The first thing I do on a new Mac is switch the Spotlight shortcut off so that keyboard switching works like it should ;-)