One can always argue "you're doing it wrong". People say the same about ror and perl. But in my experience, even with a good mvc and object model, and world-class folks, complex applications in jquery tend to become hard to maintain. I believe part of the reason is the tight coupling of state and events to the DOM.

I'm also very skeptical of the dozen-odd undocumented "extensions" to the selector language. They are useful, but tend to tie you to jQueryisms. I didn't realize for a long time that :first was not valid CSS3.