Most of the changes in the 2.7 release are visible on the back end. Readers won't notice many changes except for a few major changes to improve usability. From my perspective, the biggest front-end change is the ability to add threaded comments to a WordPress blog. Threaded comments allow a reader to "reply" to a comment and have it display indented under the original comment. This makes reading a comment thread much easier than previously available. Mullenweg noted that they didn't stop with just a basic set of comment threading. Administrators can select a variety of options with regards to comment threading. One option is the ability for the administrator to be the only user that can reply to a comment. All of the comment threading options allow for flexibility depending on the type of blog and the audience.
Other upgrades include QuickPress, which allows a publisher to begin writing a post from the main administration page. Comments can be controlled via the main administration page as well. Publishers can personalize the control panel to allow for their most comfortable settings. Check out the full list of upgrades, including the developer changes.
As I noted above, the administrative control panel is where the major changes were made. One of the interesting changes that will save time for administrators is the ability to browse the plug-ins gallery directly from a blog. After selecting a plug-in, you can choose to install it automatically. No more downloading, unzipping, and then uploading. Now with one click the plug-in is installed and ready to go.
The admin interface is also brand new and in the video I linked above, Mullenweg explains why the changes were made. As with any interface change, it will take time for administrators and publishers to get comfortable with the changes. From my perspective, the new interface loads quicker and tasks seem more intuitive. There are more options on each page so you can complete multiple tasks from multiple screens.
What I like best about WordPress is that it's always thinking of publishers and not only readers. Publishers spend the majority of their time at "home" in the admin interface and it's important to make them feel at home. I've used nearly every content management system on the market, from free systems like WordPress to systems costing millions of dollars, and WordPress just does the publisher interactivity right. Many of my sites use the Drupal content management system and while I love the flexibility Drupal offers, I find the administrative control panel to be seriously lagging behind WordPress. Drupal offers a cold, unfriendly administrative interface while WordPress is much more welcoming.
I read today that the WordPress team is already working on the 2.8 release of WordPress -- let's hope they have more goodies for publishers and readers alike!