I don't think this translates to the real world- one of the main things they did for that benchmark is add a special case for $('body') which will probably slow down (not noticeably though) most people's code.
Erm - how would it slow down people's code? We're already doing a check to see if a tag name is being used and optimize based upon that, we just added one additional check to optimize for body.
There is absolutely no way in which the check:
if ( selector === "body" && !context ) ...
Will have performance implications in your application.
Please excuse my brevity- that is what I was trying to say with "(not noticeably)". Technically, or course it will slow down code not using the conditional.
That is pretty impressive. Also interesting that FF 3.5 seems to perform better than FF 3.6 according to those charts.
Edit: Ah, nevermind, my mistake.
Other way around - be sure to double-check the raw data at the bottom (3.6 is considerably faster than 3.5).
You're looking at the IE 6 slice, not the FF 3.6 slice.