I've read the announcement about Svelte 3 today and decided to look into it.
From the announcement:
Svelte is a component framework — like React or Vue — but with an important difference. Traditional frameworks allow you to write declarative state-driven code, but there's a penalty: the browser must do extra work to convert those declarative structures into DOM operations, using techniques like that eat into your frame budget and tax the garbage collector.
Instead, Svelte runs at build time, converting your components into highly efficient imperative code that surgically updates the DOM. As a result, you're able to write ambitious applications with excellent performance characteristics.
Svelte scored high in A RealWorld Comparison of Front-End Frameworks with Benchmarks (2019 update).
Additionally, it was the most popular choice in the category "Front-end Frameworks - Other Libraries" in the State Of JavaScrip 2018 Survey.
A cursory look at the interactive tutorial shows me that it shouldn't be hard to learn if you're familiar with React. It even looks easier than React and has fewer moving parts.
Plus, the framework offers inbuilt transition effects which should make it simpler to build beautiful user interfaces.
My first impression is positive, and I'm considering diving into Svelte in the coming weeks.