It works, more or less. There's a grid/table where the dates/days of the week are across the top, and all our names/positions are down the left-hand side of the page. The blank schedule is then left out a few weeks before the next scheduled period begins and we write in the days and shifts we want to work. We all are required to work every other weekend, so on our blank schedule that's already filled in. Holidays are done on an alternating/rotating basis, so that's already decided in advance, too (unless management wants to make changes, which they always seem to do).
So, it's really mostly a Wish List of the days you prefer to work, no guarantees. Best you can do is put a sticky on the schedule begging for a certain day off if you really want it; only guarantee is to take a vacation day.
For the most part, though, it works pretty well. The last two months I only had a couple of days switched around on me, and neither was a big deal; management makes requests for additional days or switched days as needed, also no big deal, you can refuse once the self-schedule's been approved
I prefer this system, actually, to being scheduled without any input for regular days each week. Since I only work 3 12's, I'm glad to NOT be on an automatic schedule; I often find I need different days off each month and would constantly be trying to switch with someone.