So the question (for me) of size/speed comes down to: is it faster/better to build my own jQuery UI js file with selected components or to use the full file from Google's CDN?
The former option has the benefit of being smaller, while the latter has the benefit of being hosted by Google's fast servers and there's a decent probability the client already has it cached.
when using jquery and other google hosted frameworks, i tend to use them from google CDN because a lot of the time not only is it faster, but it tends to be faster for traffic from all over the place. i have a site hosted in hong kong and most of the traffic is from japan, africa, and south america, so obviously the performance will differ for different users. but when i use jquery from google CDN, the performance tends to be similar across users.
For anyone curious about the quality assurance effort that goes into jQuery UI, take a look at the history of the new autocomplete widget.
I have been following since it was an standalone plugin, and the author cleaned up the design and code so much just to qualify for inclusion into UI. Perfect.
It still (like most of the widgets) only goes 90% of the way and lacks things like gmail/facebook-style multiple items by comma separation. The worst thing is that the properties exist (multiple: true) but are not utilised as yet. Instead when an item is selected you have to dump it in a recipient field.
Alas, this is still a themed UI framework that doesn't style ubiquitous basic form fields like checkboxes and radio buttons, although they do get points for adding button support this time and (if I understand the hints on the linked page properly) planning to add more in future.
Curiously, ExtJS seems to have similar limitations: you can style all kinds of things, but there doesn't seem to be any support for theming of the most basic UI controls.
Curious, does the Google CDN version contain all widgets, effects, and themes? Or what?