Surprised this is done in Rust. I could never imagine not doing the v1 of something like this in Python or similar, to be able to change things quickly. Maybe the design was very clear on the person's mind.
Even though Python is the language I’ve used most, I wouldn’t want to use it for something with a lot of uncertainty and that will suffer many changes. Type systems make it so much easier to change things early on without breaking everything. I’d probably pick F# or similar.
Most of the developers (some of them being former Mercurial and Git developers) including me generally seem to like it. Based on my own experience, I think it's a pretty excellent choice, but I'd be a bit biased as a die-hard Haskell/C programmer for something fast with types.