FTP Server with Ubuntu 9.10 Server

I still use FTP. Mostly because all the other methods I looked at (WebDAV, SFTP, and Web Based file server) were all missing one thing or another that I feel I need. I have the following types of needs:

• I need a ftp location that a user can upload into, but not download or see. (Drop box)
• I need someone else with the ability to download and delete files from that dropbox
• I need an group that can read/write one particular folder (shared workspace)
• Another group that can access that same shared workspace while also giving access to another folder with read only permissions (Library).
• I need a group that can access the same Library folder mentioned above. But not access the shared workspace.

I had other types of configurations which I decided I could drop from the requirements for now just to make my life easier.
Other requirements:

• Minimal configuring, management, trouble shooting for individual users
• per user bandwidth control, 
• nat support, 
• simple client instructions/requirements, 
• and for most of the shared files to come from a SMB NAS.

I have used a windows FTP server for over 5 years to achieve all of the above. The windows FTP server I preferred was called bulletproof or G6 depending on how far you go back. It is actually an excellent server that I recommend to anyone in the windows world. Here are some of the features that I used:

• Virtual Users (A user list managed by the FTP server instead of the OS)
• Virtual Groups
• Per User/Group bandwidth throttling
• Easy user setup by just picking their group.
• Chrooted Users (Keep the user from getting to the rest of your file system)
• Virtual Links and Link traversing
• Virtual Folder Permission control
• Nearly all folders on a network NAS device (Buffalo Terrastations)
• NAT Traversal/Passive FTP
• Non Standard Port
• etc.

In the next FTP posting I'm going to show how I came close enough to these features in Ubuntu 9.10 Server to eliminate another windows machine using Pure-FTP. Surprisingly there wasn't just one hurdle for accomplishing this, but nearly every feature had to be painfully worked out. On the plus side I have more features than I had before and I have better options to manage the server.