If you will permit me to tout things I worked on while there, Opus seems to have been pretty successful? The final story has not yet been written on AV1, but it is still the best chance we have had for a royalty-free video format and thanks to YouTube, Netflix, Facebook, etc. now makes up a non-trivial fraction of the bits on the internet. That ought to be enough to get it over the "ever remotely panned out" bar. I find myself using WebRTC quite a bit these days, too, so happy to have been a (small) part of that.

>Idk, Rust seems to be working out.

Rust was created to write a new rendering engine in, which they abandoned half-way. Then they abandoned Rust itself.

And, guess what, they also abandoned Thunderbird:

"Thunderbird has been independent since 2012. See https://blog.lizardwrangler.com/2012/07/06/thunderbird-stabi... Many people have not realized this, but for Thunderbird to grow and adapt to a changing environment having some sort of income stream is important. There is a limit to what the volunteers can do. Hence significant fund raising efforts. The web site perhaps answers the current arrangement best. https://www.thunderbird.net/en-US/about/ One of the issues we face is that people in general do not differentiate between Mozilla co the commercial entity that produces Firefox and the Mozilla foundation that owns it. Thunderbird's arrangements are with the foundation, not the company."

Rust is a Linux Foundation project, and the process of adding more Rust code to Firefox is (to my knowledge) less of a priority. I love Firefox, but Mozilla enjoys shooting itself in the foot too much.