I strongly agree. I don't think a website is going to do anything with my user agent string that benefits me. I'd much prefer a web where websites can't do things outside of the standard. We ne er needed webmidi, but a company that makes a browser/is hybrid definitely wanted it.

Speaking of Google, won't this interfere with their "look we're not a monopoly" payments to Mozilla Corp?

That's the sort of this that should be illegal for anticompetitive reasons.