This is a tough one for me.  While I want to fight for every byte I can, I understand the design goals around making the UX more consistent and more usable.  

By striping the legacy and other redundant/useless code, I was able to get the file to 20k.  This is fairly small on the grand scheme of things especially if compressed.  It would take a couple releases to get to this size according to policy.  This could be a bit easier to accept if one designs to reuse the styles as well.

The bulk would felt be even less if DNN Corp brokered a relationship with a CDN to host the common assets like this . 

For the most part, the big additions are for core items like the new pop up boxes and admin tabs that will be viewed by anonymous visitors.  If developers grab on to the UI elements then many modules would look a ton better.

I can say I’m happy to not the full breadth and width of jQuery UI being used (IE the miles of icon definitions and theme bloat).

To get any better and still have a solid UX design, DNN would need some type of smart CSS content handler...

(Sorry about the cheekiness)

Agreed which is why it is wise to employ a fall back method such as the one I suggested here

Free is a good price

Background: separately, I have suggested it would be fantastic if Corp were to broker a relationship with a CDN whereby core files could be offloaded in exchange for advertising. I first saw this with jQuery Tools not to speak of Google and Microsoft helping out big libraries like jQuery and Mootools.