Best practice for announcing new features
I recommend you to put new features both in history and "Additional info", that's the easiest way to inform users about new features. Also, you can implement code in your user-script to notify users about new features, but that's a little harder.
Right now I am putting a lot of work into a hotkey based userscript for LinkedIn I'm working on (it helps that I was recently laid off and have a lot of time at the moment).
The GF history is pretty good, but I don't know if folks actually read them to know what things were added; things like new pages and new keys, mostly.
Do other folks just let users silently discover new features? Or do they somehow track what version users were running before and offer a What's new view or indicator? Or is that something folks leave up to the userscript manager?