I'm not being smug, I really want to see some benchmarks that make sense. The only thing I've seen is either "jQuery version x.y.z. is % faster than jQuery version a.b.c." or "jQuery is % faster doing something than Prototype." Yes some of these libraries may be getting less slow, and some of them are less slow at doing certain things than other slow libraries, but the only thing that would make sense is to compare them to hand-written JS and see the trade-off in performance vs code size.
Most jQuery application code I see is just adding layers over the DOM in a way that doesn't provide any extra expressive power or conciseness (frequently the opposite).
Yes, selectors are cool, but only if you need to manipulate a document that's been generated by someone else. If you have control over how you generate HTML, you can actually keep track of your DOM elements in a way that doesn't involve searching at run-time and expresses domain concepts - I mean, imagine this!, actually program normal code.
They are fast because they have been coded by experts. So maybe they look cute - would your code that looks as cute run as well? Probably not unless you can match them in knowing why.
Or by leveraging their work as their documentation suggests.
Seriously, performant javascript is not some magical thing only wizards can attain. Performant _generic_ javascript is tough stuff, but just using the libraries is hardly JIT compiling.
And yet JQuery and Mootools are both incredibly fast, as benchmarks show.
And yes, I'm aware of the model you're using, and reiterating explicitly what I implied isn't making your argument any stronger, in my opinion.