I was kind of hoping it was a better type checker, something like mypy + pyright. To be fair that's an incredible amount of work, so maybe we'll see that later. Still very excited.
That was actually my first guess, and while I certainly would love to see that, packaging is such a headache for so many people that this could be amazing. Even with poetry I still occasionally get mysterious errors and wildly wrong resolver claims about versions not existing.
Why include mypy at all? Pyright is amazing and all you need.