1. Saeed is writing a really nice series of articles starting here: https://www.visualstudio.com/learn/git-at-scale/ In the first one, he lays out how we think about small/medium/large repos. Summary: size at tip, size of history, file count at tip, number of refs, and number of developers.

2. Fairly confident, at least as far as usable repos go. Given how unusable the Windows repo is without GVFS and the other things we've built, it seems pretty unlikely anyone's out there using a bigger one. If you know of something bigger, we'd love to hear about it and learn how they solved the same problems!

3. Windows is a 30 year old codebase. There's a lot of stuff in there supporting a lot of scenarios.