Like the title says. Is there any way to disable the bar on the Apple TV, or for any other set to box?
Yes, like the other person said, down arrow button will bring down the status bar.
Also, when watching a movie or TV show on Netflix, press and hold the "select" button on the remote. A screen with subtitles option will come out and you can choose English from there and continue watching your show without interrupting it. Not every show and movie supports the feature but it works for most newer shows and movies. I discovered it by coincidence when watching White Collars episode. It looks better than the Apple Tv's subtitle option that you activate from the settings. You may want to turn off Apple TV's own subtitle option off to avoid overlapping each other.
You should experiment with the buttons while doing different activities. For example, when watching a show or movie, pressing up arrow button twice will bring will bring the info for the TV episode or movie you are watching. (Pressing it once will bring the status bar).
Pressing the down arrow button twice divides the status bar in small chapters for an alternative fast forwarding or rewinding.
Pressing and holding the select button while listening music from either iTunes Match or through home share will give you different browsing option (by artist,etc) and will also allow you to activate genius for your music.
You may not have many buttons on the remote but they are highly functional. Happy experimenting