They specifically refer to the basic JQuery UI elements when they state, under "Essential tools for modern websites"
<blockquote>
Let's face it: do you really need drag-and-drop, resizables, selectables or sortable tables in your web applications? Websites are not desktop applications. They are different.
What you really need are tabs, tooltips, accordions, overlays, smooth navigation, great visual effects and all those "web 2.0" goodies that you have seen on your favourite websites.
This library contains six of the most useful JavaScript tools available for today's website. The beauty of this library is that all of these tools can be used together, extended, configured and styled. In the end, you can have hundreds of different widgets and new personal ways of using the library.
</blockquote>
This looks like repackaging the more popular stand-alone jQuery plugins/widgets into a single bundle/distribution, with nice docs and demos, very different from jQuery UI which is more like half a framework and some widgets.
And I have to say that I agree with them.
Whenever I am confronted with, say, a "window" in a web app (i.e. a popup that I can move around in the browser), it just feels weird.
Some of the tools look like great implementations, but if I ever saw a website use the "expose" tool (http://flowplayer.org/tools/demos/expose/index.html), I'd be pissed. It doesn't seem to serve much of a purpose, except perhaps for a first-use help screen, and even then, it's disconcerting.
It's useful for videos to minimize page clutter when you're not watching full screen. Hulu does a similar effect when you hit "Lower Lights" next to a playing video.
...that doesn't behave like any other lightbox anywhere. This Expose tool is just flat-out bad UI; it emphasizes something, makes the user guess how to deemphasize it, and isn't visibly for anything.
I think the library itself has great video support but not much else.