I really like it. Replaced Vue with Svelte and things have been great so far. Smaller bundles, and much lighter components. Built-in state management is very handy.
The initial pages are Go templates which are hydrated with Svelte components. It took a bit of trial and error to get the flow right so that I don't have to write double the code.
I don't know if it's the next big thing or not but it works really well for me.