Had it done about 12 years ago for kerataconus, at the U of M hospitals. Tried correcting it with a hard lens, just couldn't get one to fit comfortably, it was warped too bad. The only bad thing about the surgery was that I was awake during it, and when I started thinking about what they were doing, I freaked out a bit. Got myself to settle down, though.
The eye settled down to about 20/40 (it was estimated at 20/300 before the surgery) after a year, maybe a bit more. Every time they took a stitch out, it would change slightly. It's still got some astigmatism, but it's correctable to 20/15 with a Toric soft lens. It was quite amazing how much my eyesight improved immediately after the operation - the next day was 20/70 uncorrected. I was told that they had quite a cornea bank, I had the operation scheduled about 2 months in advance.
I was told they believe it is caused by eye rubbing, as they see it in people with heavy allergies and those with Down's syndrome. I only had it in one eye, which they said was pretty rare, also. I go for a yearly checkup for it, and they say it looks great. Had one bout with rejection about 3 years afterwards, but it was cleared up with eyedrops. I've asked about Lasik to cure the astigmatism, but the doctor doesn't really recommend it since I've had the transplant.