Depends on your definition of fine. In certain cases it would crash browsers on load, in other cases it would deliver a solid 60fps. I think 3d on the web does need a bit more polish so that it's a good experience universally.
The Unity engine has been outputting WebGL builds for years, and having played a bunch of them (and deployed a few myself), I've never once seen a problem that didn't exist in other builds of the same game
