The most popular feature request was to tunnel over S3 buckets. I was surprised it worked. The latency is high (3 seconds) but the bandwidth is high enough to stream a 1080p video from YouTube. Overall, it has similar performance to internet through geosynchronous satellites.
The upgrade took the better part of a year and the trickiest part was catering for the various ways the file systems synchronise. Some are fast, some are picky about open file handles, some require IO operations to be retried.
My favourite aspect of File Tunnel is people using it in ways I never anticipated, such as:
* Allowing two VMs to communicate without networking enabled (via VirtualBox Shared Folder)
* Providing internet to a remote RDP session by creating a reverse tunnel to a local SOCKS proxy.
* Controlling a vending machine through an FTP server meant for beverage logos.