I did it in college (5 years ago) a lot on the grass playing soccer and rugby. I started running on pavement (with shoes) afterward and was killed by knee aches and achilles tendon problems. I connected the injuries to the pavement, not the shoes.
Now I hear that maybe millions of years of evolution actually makes humans really good at running without shoes, so I decided to give it a go unshod.
Went almost a mile today on a pavement track, and it was a bizarre experience. The motions and muscle movements were all completely different. But I liked it. My feet and legs are very strong so I didn't have any problems with weak feet. It was just different motions.