We introduced some opt-in telemetry in dolphin-emu.org several years ago. I remember several times we discovered things we would likely have completely missed otherwise:
- We found out by looking at the distribution of software version that we had a strong holdout on one specific revision. It turns out we had a regression in a niche feature which was very important to a sub-community of our users, and users were basically telling each other to just use that old version. No bug report was filed until we found out via analytics and asked.
- We have a "game quirks" mechanism where the emulator reports weird edge cases that happen very rarely. Current list: https://github.com/dolphin-emu/dolphin/blob/master/Source/Co..., example usage: https://github.com/dolphin-emu/dolphin/blob/ffdc8538a162b1ca... . We used this to find games that use currently unimplemented or stubbed features.
- The list of popular games being played on the emulator was extremely surprising because it turns out there's a huge disconnect in what most NA/EU players are playing and what JP players are playing. This led to us adding a bunch of new games to the list we regularly test for performance and stability regressions. Would you have guessed that Inazuma Eleven GO: Strikers 2013 is in the top10 of emulated games on Dolphin?
