The prob people have with serv-u is not the prog, it's the user .. I have been using if for years and have never had a prob with it .. it is very easy to set up and is the best app for using as ftp server, I have found the only issue I have with it is that it don't work well with Passive mode range behind router, so you are stuck using port 21 ...
Check to see what your ip is - Make sure you know whether it's dynamic or static ... Either way the best thing to do while using an ftp server is to get a redirect (dyndns.com is the best one and it's free) - when you get a redirect all you will have to do is give people the url you chose ..