As much as I love jQuery, I feel it can quickly become a crutch, particularly for those who have spent a fair bit of time relying on features like .animate(). Modern browsers often have alternatives that (depending on the situation) simplify your code and offer significantly better performance. Similarly, I cringe whenever I see jQuery UI pop up in an interface - while it's easy to use, it also keeps some from developing UI features of their own.

There's a time and place for everything, and as a whole, I feel many are over-relying on jQuery.