Its the best to me because:
I messed with it a lot in Tribes 2. So I can only assume it has gotten better but:
Its net code was not tied to frame rendering and was object oriented from the get-go.
Had a built in world editor that worked while live games were running. You could prop a server up and edit the world real-time.
Supported scripting and compiled it on the fly for faster run-times
had the best vehicle code I've seen outside of a racing game...
Hopefully one can learn this, perhaps consider publishing, and then license it for $100 still. That'd be great!