I love pure JavaScript. jQuery is overrated and most libraries are only good for one thing or the other, nothing can replace the joy and performance of Vanilla JS!
jQuery is kind of a big download for mobile, so I often skip it for small tasks.
What gets me is when people include jQuery and then further bog things down by loading a lot of plug-ins to do things that could easily be accomplished by adding a few lines of code of their own. Even if you do need and include jQuery, it doesn't mean you have to use it for every piece of javascript in your app.
Many times, a plug-in will do a lot more than you need it to do. If your primary goal is to just get rid of the 300sm delay translating tap events to click events, you don't need a library for full gesture support. You need half a dozen lines to listen for touch events.
If you just need to add some client-side persistence for a few basic things in LocalStorage, you probably don't need a plug-in with a complex query syntax.
Cannibalize a library if you need to and pull out the bits you need. You don't have to include the whole kitchen sink.
> jQuery is kind of a big download for mobile, so I often skip it for small tasks.
That's what Zepto[0] is for: jQuery's API, 20% of the size (although it drops some features, e.g. $(selector) is pretty directly proxied to document.querySelectorAll, so $('> .foo') works in jQuery but blows up in Zepto)
Ah, last I looked at Zepto, it's support for non-webkit browsers was pretty lacking. It's good to see they're making strides on the cross-platform comparability front. The supported browsers list looks pretty good now.