I haven't cut my finger using the cutter but I have cut it when I have forgotten to click my blade back in and brushed against it.
I teach my kids in class how to use the rotary cutters and it freaks me out every time they do, although no one has ever cut themselves. Then, at the sewing expo in WA this year, I found the Gypsy Grippers. I bought several of the "inbetween" size, we use 24" rulers in class and they work perfect. Keeps your hands off the ruler, away from the edge and the cutter. Gave me a TRUCKLOAD of peace of mind.
You can see them on www.thegypsyquilter.com.