(Disclosure, I worked on this product in a previous life) So this is an enterprise CMS example, but the UI did get some pretty decent feedback from customers.

Have a look at http://media.vignette.com and you can see some screenshots. This product was targeted towards media companies (Gaming companies, Online media/news sites, video producers etc) so it did allow us to focus on some specific needs. You can imagine that with the volume of content that news sites produce, their requirements can be a little more high-end that your average user as they can spend 6-8hrs a day in the tool.

After designing and implementing quite a few CMS platforms, I think it is pretty hard to come up with a UI that will be appropriate for all users as many of them come to the tool with very different tasks in mind. Think about the legal guy or manager who just needs to approve something, the creative team who needs to upload some assets, someone working on a page or content, a marketing person who just needs to put some promotions on the site. Even within a media company there are people with pretty distinct roles and tasks they own. Therefore in our last UI we built the notion of workspaces...there was:
- a Review Workspace which had an optimal layout for reviewing and approving content
- an Asset Workspace which was optimised around batch uploading media, resizing it, a filter based UI because the library of images/videos tended to get pretty large
- a Marketing Workspace just for the marketing team who is normally responsible for creating new promotions, and then deciding where they go on the site. Not every site needs this, but for those that do it worked pretty well as the marketing team just saw this workspace when logging in and didn't have to learn or care about all the other areas of the CMS.
- And of course don't forget the Content Workspace where you can create content and pages :-)
- For smaller shops, the workspaces are all accessible to multiple users, it is just the notion of the right UI for the task as opposed to one UI for all roles and tasks.

Not suggestion these are universally appropriate or right for your customer base, but I think on close examination you'd find at least 3-4 profiles of users or common tasks that can be optimised. The result for optimising for the 80% common tasks in this system meant that certain complex tasks could be done in <5 clicks. While I personally rate WordPress very highly for UI, the users we were designing for used this products for many hours a day and they felt WP was too many clicks, especially for media handling.

I've probably droned on for too long already and so there is not enough time to list every UI tweak and feature we created, we spent 2 years on the UI, but here is one example.
Dynamic UI Controls based on dataset size: A common problem with a number of CMS tools we found was that the UI designer made a guess about how much data would be in the system for a certain task, and then design a UI control that might work great for 10 items, but would be useless if there ended up being 10,000 of those items in the system. So we built some UI controls that would adapt to data volumes...say you had content type x and there were only 10 of the items in the system, you'd ideally want to present it with a set of radio buttons (assuming select one requirement)....more than 10 but <50, popup/overlay with all items listed alphabetically on a single page for quick selection, 10,000 and you're going to need some type of navigator or set of filter controls.

P.S. Don't confuse this with some other previous Vignette products which have a pretty poor UI, this CMS was specifically created with a new UI from the ground up for that reason.