A good chunk of the passwords use MD5 hashing, I think it's the early ones. Those have already been cracked and posted online. The later ones, those past 3000 or so are indeed salted as far as I know. But either way, it's much safer to change passwords once mtgox is back up. Also, mtgox should go to great lenghts to assure people this will never happen again.
Looking at the csv file, it seems that all accounts beyond the 3040 mark have "$1$" in the beginning of them. And many of the ones prior have it as well -- probably those who changed their password after the salting feature was added.
The benefit provided by using a salted password is rendering a simple dictionary attack against the stored values rather impractical provided the salt is large enough. That is, an attacker would not be able to create a precomputed lookup table (i.e. a rainbow table) of hashed values (password + salt), because it would take too much space.
http://en.wikipedia.org/wiki/Salt_%28cryptography%29 