I've had them before. One of them was too large to pass and I had to have it surgically removed. I went like five years between that one and one that I had earlier this year. I was able to pass the second one. A little blood in your urine, and it hurt a bit when I passed it, but as soon as it came out, it was instant relief. Just make sure to drink plenty of fluids to help flush it out.
The way it works is whenever you feel intense pain, that means the stone is moving. Once the stone passes into your bladder, you're home free. Your ureter (the lines that run from your kidney to your bladder) are much thinner than your urethra, so a lot of times you'll pass the stone and you'll experience a lot less pain than when it goes from your kidney to the bladder. Sorry if that's a bit graphic -- like I said, I've experienced two really shitty ones before. A lot of times people pass stones and have no discomfort at all.