Good point, although I find that performance is always an issue—even when I'm plugged in. I'm also a tab hoarder (though more in Firefox, thanks to Tree Style Tabs), and I find that my Mac's sluggishness is always caused by having too many tabs open.

Sadly, my workaround has been to quit and re-launch browsers, which presumably has a similar effect to this update. Looking forward to seeing if the new version keeps things snappier...