I haven't had an ftp server for a while now....but I used to have one on my computer at a friend's house on his line (pretty fast cable modem).
There were times when we had 30 or so users logged in at the same time.
First we tried serv-u, and that couldn't do everything we wanted.
Then we tried Warftpd. That worked great, and it's customizable w/ the macro's. Has upload verification, tons of options, setup, customizable, and best of all, what I liked best - groups!
Now I hear of this g6 ftp server. I think it's probably the best, from what I hear - has resume upload, which other ftp servers don't have. I haven't used this yet, but if I ever think of having an ftp again, I will be using that one for sure.
You might also want to try vermillion ftp, and the built in one for win2k / nt if you have NT. I also heard that IIS is the best, since it does FTP, http, news and mail all in same single server - a brilliant invention.
Serv-u is $30 to $40 i think, g6 ftp - i am not sure, and warftpd, as stated above, is freeware at
www.jgaa.com.
Hope you find the one that works for you!
Tib