Performance is good, but I would only use it on well-bounded target audiences. Anything over 10000 simultaneous users on a single instance would probably start to concern me. It is perfect for any internal or B2B UI you might want to build.
That said, combine Blazor with other Microsoft magic like Orleans, and you can start to horizontally scale. Might even be possible to make Server-Side Blazor viable for mass public consumption using this approach.
Edit: It does appear this would be fairly easy to rig a test for as of latest versions of everything. Should be able to throw Blazor and Orleans on top of the same IWebHost instance.
