I used to use leechftp, I had some problems with it - I hate how it has "failures" and gives up on certain files, and it always gets me banned from ftp servers because it hammers them.
before I used leech, I swore by flashfxp, great program. only thing was.. I had an. *ahem*.. ahh not-so-legal registered copy, and it kept warning me that it knew I had an illegal registration # and as I read this, flashfxp was calling the swat team to my house to pin me to the wall and blow my brains out or something.

basically it was just annoying.
but since, I've tried it again and I don't get that crap. Yet.
one thing I liked about cuteftp and leechftp, that flash doesn't seem to have, is storing of ftp server "favorites" with my account info, etc. there is just a history feature on flash, but that doesn't help me much