First let me say that while I do not like the new version I appreciate the effort that went into it. With that said it's clear the majority of people here seem to dislike completely or to some extent the admin panel. What I found disturbing was the attitude I read if you don't like it too bad. I also read a post that stated if you don't like it get involved. That is where the communication break down occurred I truly believe.
I went back and read the developers posts here. The single most blaring issue I could see is no one had input there from the end users. It seemed like a bunch of devs saying this is the new system and they are going to have to like it. Not a good business practice, Yeah don't give the that change is inevitable blah blah.. This isn't a consumer product that needs flash and colors in the back end, it's a product that needs to be lean and fast. As has been stated here many times before "if it isn't broke don't fix it". I say simply tune it up.
I run several large e commerce sites based on WP and Woo commerce. The new update basically obliterated the product pages on these sites. SKU numbers were all out of whack, because of the new color pallet certain product bubbles were missing etc. I alerted Woo to the problem as of yet they have not released a fix. Woo does not allow you to edit the CSS code so it's truly broken. Yes I installed the plugin to return the admin panel but this is only good till the next update blows something else up.
Not once did I read anywhere of concern for the end user having issues. It was more about how cool this is going to be and how we need to stop calling it MP6, or concern that the seaweed color theme makes the cut. Now I wasn't privy to the phone meetings and the devs don't post the minutes of those so I can only address what was posted
WP is so much more than it's original concept now, BUT work flow is the most critical. Just because some interface is the "trend" doesn't mean it has proper work flow. As a software developer your goal is not to make something pretty, but something that is conducive to helping the end user be more productive. The mere fact there was little or no forethought given to the fact during the design that some users might need that old admin panel design makes this totally evident.
In all reality what should have happened was 3.8 should have been pushed out with the old style admin as default with the option to use the new interface. It would have satisfied all parties in the matter while allowing you to test the new platform. That way you could have collected meta data on what works and what doesn't without breaking the end users sites.
The other issue you may want to reconsider is auto updates. This is a very bad idea. Imagine an e commerce site or a high traffic site taken down by a pushed update and no way to roll back. Wow that's a disaster waiting to happen. The worst part would be that it would keep breaking itself over and over because WP would keep trying to auto update again and again.
Thanks for your time