Haven't had the chance to be a player much. A couple one-or-two shots which I've played across the span of 1st to 11th level. I have DMed one party up to 12th level, ran one party at 11th level, and DMed several parties up to 4th or 5th level. So I answered 12 for the poll.
Never DMed or played characters up to 20th, so I stand in awe of those of you who did this successfully.