I double checked a GPU capture after the mix-blend rewrite got landed, and I see nothing worrying. The red frame indicator is stable most of the time. We end up with around 77 draw calls, not that much pixel work, etc.

I agree - I also checked this page with your MBM changes, and it seemed much better than it used to be.

Yeah it's most impressive, between picture caching and the mix-blend rewrite, arstechnica.com is night & day. On my MacBook Pro scrolling it used to redline my GPU and give about 30 fps at 1280x800. Now today my GPU hardly breaks a sweat and it's butter smooth at 60 fps. Both examples were with an opaque GL context. Well done & thanks!