Using nothing but a packet sniffer on my cable modem connection I was able to pick out the name and password in clear text from most FTP logins. This represents a clear danger to any machine that you put FTP on.
Are you aware of this issue? If so, even the supplied FTP server will do fine. As to ease of use it's no harder than any of the Windows Server product.
As to the Web Gui, you'll have to write that since it's not part of the package.
Can anybody recommend some easy to use (and maintain) FTP server software to run on a Windows 2003 Server? Cost is not really an issue but ease of use and the ability for clients to log in using any browser is important. A good looking easy to understand graphical interface for uploading and downloading would be even better.