Note that Site Isolation isn't on by default, and I still don't know what they're going to do about sites that contain hundreds of cross-domain iframes.
My point with site isolation was more their continued effort to push interesting, compelling security improvements. Currently, from a corp perspective, enabling site isolation for internal high security websites (SSO pages etc) is possible with GPO and a big win imo.
Please don't take it the wrong way, I think Firefox is awesome too :)
Please don't take it the wrong way, I think Firefox is awesome too :)