Not really sure how to answer that exactly. Fast enough? :-) Performance is one of our top priorities for Flutter (basically priority #2 after "correctness"). There's still plenty of opportunity to optimize, though.

Honestly, so far we haven't found that Dart's intrinsic performance is an issue for Flutter. When we've investigated performance issues in the past, it's usually turned out to be around graphics or bad algorithms in the framework. Our most recent performance issue was related to compiling shaders on the fly; turns out if your shaders are super-optimised to render scenes really quickly, they can end up being so expensive to compile in the first place that you miss a frame or two when you first try to show the scene.

> I heard here that it enforces static typing

Sort of. It's more that the compiler does type inference if you don't specify types (as opposed to just not having any static types). You can still explicitly specify "dynamic" as a type, and generally if you just don't mention types it feels dynamic, still. (The Flutter framework itself always specifies types explicitly, because that helps catch bugs earlier.)

> I assume for performance reasons.

As I understand it, it's partly for correctness reasons -- it makes it much easier to catch bugs -- and partly for performance reasons.