Yes, most will agree that the admin design of v2.5 was a fail and v2.7 "healed" that. And also in this heavy contrast lays the great feedback that v2.7 received.

However, you're painting a picture here that this version 2.7 was made by the community "mostly". I don't see it that way; "we" the users were given some surveys, yes, and that was new and great, really! In the end, however, it was a small group of core developers or "influencers" who made this release. But a few surveys aren't a big community effort, if a small group still makes most of the work...

I have voted in this one (or were it more than one?) survey about the admin icons, it was fun. I voted for the icon schema submitted by a German agency, which was second place in the overall voting and ended up being used for the blue color scheme in the admin.

In my opinion, the fall release of 2013 with the new admin styles and the former "MP6" plugin were as much community driven as the 2.7 release - if not way more! Because of the widespread MP6 usage of the feature plugin, the users, the community could "smell" this release a lot more before and a lot of feedback found its way back to the "developer circle".

Every way of working out such releases has its advantages and its downsides of course. Given Matt's new strategy and tactics for the next releases/ cycles I can't wait what fruit is coming out of that. I hope for matured releases, that will have impact again for the long run (like 3.0 for example). It's time that half-baked, slow solutions like the Customizer get a makeover/ rebuild, so that's finally worth it. And if it's not worth it, then cut it off and let new/ better ideas mature!!!

One thing the 2.5 - 2.7 era shows: sometimes you need more than one iteration to hit the nail right. So let's hope for next group of releases!

Here's my little list of areas where WordPress should improve:
- frontend search!
- admin search!
- user management, user groups
- editor/ writer tools, post status, whole publishing process
- badge installing of plugins
- make widgets no longer as options in the options table but somewhat better, maybe transform into a post type or whatever --> widgets as a flexible concept of content blocks, however, are awesome! :)
- ...