Valid points. I think each new feature will likely interest a different set of developers, so the feature can still get pretty wide testing even if a lot of developers choose to wait for it to mature, or choose not to use it at all.
I do agree with your points about the rapid release of browser bugs alongside the new features. I've had multiple occasions where clients have told me "You changed something and broke the site" on a project I haven't been working on, only to find out it's only broken in Chrome. My response to them that it's a bug in Chrome that's been reported, affects lots of websites, and will probably be fixed in a few days/weeks, and there's little or nothing I can do about it, is never satisfying.
I do agree with your points about the rapid release of browser bugs alongside the new features. I've had multiple occasions where clients have told me "You changed something and broke the site" on a project I haven't been working on, only to find out it's only broken in Chrome. My response to them that it's a bug in Chrome that's been reported, affects lots of websites, and will probably be fixed in a few days/weeks, and there's little or nothing I can do about it, is never satisfying.