In Chrome it seemed to delay the time it took to get a smooth page scroll, I'm running several adsense ads loading in ascync mode and some amazon stuff so maybe its due to that.
Maybe it added just that one more thing to load. Just seemed to make the page load seem heavier. I also run W3 Total Cache so maybe an issue there to tweak in script load order. The WP tabs adds in another css and js file to have to deal with. Sometimes it's easier to just forgo the bells and whistles like a tabbed ajax widget for a site like mine with lots of other stuff going on.
I'm trying to do my best to speed page load time but at the same time keep the existing ads. The Schema theme has given me nice improvements there and I'm quite pleased. Very few quality and visually appealing theme shops think about SEO, ad placement and load time, glad I found you.
Other issues I found with it.
-I don't like how it goes translucent when switching tabs.
-When using three tabs the Comments Tab title text would get jammed up against the container box on portrait tablet resolutions.
-The tag tab shows all my sites tags. I have a lot of posts and many many tags so it filled up the side bar for quite a distance, Didn't see an option to show most used tags to shorten that.