I did that. I didn't have it "in hand," but it was on my computer, ready to have the date edited. I was required to give 3 months' notice, so when my friend told me on February 24th that May 25 would be the best start date for our road trip together, I submitted my letter the following day. I had been planning on doing it, and had another job in the works, but I just needed that last little push over the edge.
It was almost disappointing when no one freaked out over my leaving. But I guess they were used to it; the turnover in that place was so ridiculous that after 3 years of working there, I was the 3rd most senior person there (in terms of longevity), out of about 25 people. And one of them only beat me by a few months.