Care to share some highlights? Fifth to second sounds like a big difference!
I was under the impression that type checking was not one of the goals of PEP 484 etc.
In C#, the using statement combines with async/await. It is cool that Python finally gains proper async/await, there is no need to diss other languages.
Using it you can safely cleanup/commit transaction/release lock/etc when exiting a block of statements (even if an exception was raised). Plain 'with' statement cannot call asynchronous code in '__exit__' methods, 'async with' can do that (in '__aexit__').
An edge over what? You're still limited to a single thread via the GIL. Until that problem is solved, Python is certainly not the best bet (all else aside) for server development.
Do you really need to share mutable state between threads in your server? If yes, what's your story when you'll need to scale to multiple servers?
If not because you can keep shared mutable state in a separate service (DB or similar), you can deal with one-machine scaling very similarly to scaling across machines - just start/fork a process per CPU. You get simplicity, avoid the whole thread-safety can of bugs, and all the administration benefits of stateless servers.