I think they run a bit big, personally. I haven't tried them for me, but DD has a pair and she kinda swims in them. As a PP said, though, they come in combo sizes, so DD is in a 10/11, even though she wears a 10. I'm hoping they fit by summer.
I think they run a bit big, long, but more narrow than original crocs. My feet are narrow and I wear a size 9, I bought a size 8 in the croc mary janes and they fit perfectly! My dd has a chubby foot and much prefers her reg crocs.
I am thinking about getting a pair of the MJ's. Do your feet sweat in them though? (I have a pair of regular chocolate croc clogs I live in with none of the air holes and I can't not wear socks with them-one of the rivets broke though so I am waiting for replacements!)