Geographic usage
The vosotros form is used on a daily basis in Spain and rarely even heard in the rest of Spanish speaking world outside of church and in books and films that come from Spain, although people in other Spanish-speaking countries do understand it. Spanish speakers outside of Spain only use the 'ustedes' form for both formal and informal you plural.
Should I learn it?
If you are going to spend time in Spain, you must learn it. If you know with absolute certainty that you will never ever speak to anyone from Spain nor read any sort of literature or newspapers nor see any Spanish films nor listen to any Spanish music, then yes, you are safe to ignore the vosotros form.
But seriously now, in order not to be taken by surprise, you probably should have some basic familiarity with the vosotros form. As stated, native Latin American Spanish speakers understand it, although they don't use it and probably couldn't tell you the verb forms themselves. You should at least aspire to this level - understanding - even if you are in a situation where you will almost always be dealing with Latin American Spanish speakers. Our own
Spanish Whiz computer program lets you choose whether or not you want to practice the vosotros form in the verb exercises.
