Flow's Windows support is pretty buggy. We have some team members who prefer Windows as their dev machine and it looks... painful.
Flow supports the upcoming `?.` operator and overall they seem more open to introducing features that are in a development phase and might be changed/deprecated in the future. I guess it's a matter of perspective if that's good or bad, but man I'm going to be sad if we end up making the change and I have to convert all those nice and clean `foo?.bar?.baz` chains into some unreadable multiline monstrosity or calls to some random getter library.
Flow's exact object types [1] are really useful and have prevented actual bugs when used with optional properties. TypeScript's concept of "freshness" [2] does prevent many if not most of these bugs though.
[1]: https://flow.org/en/docs/types/objects/#toc-exact-object-typ...
[2]: https://basarat.gitbooks.io/typescript/docs/types/freshness....