I have two perspectives to give since I work with two separate publications: Imprint is a daul-print/online newspaper (currently powered by a heavily modded version of Mambo), and The Boar an online-only publication.
For both, most of the writing is done primarily offline (i.e. Word), and copy-pasted into the CMS. In the case of Imprint (the newspaper), it's written offline first, laid out in InDesign, and then copy-pasted over. This is not really optimal as it's a tedious task that no one really wants to do. I did some work on potentially trying to ease the pain of uploading content from the print edition through some clever scripting and plugin development. Bugs aside, it wasn't really a good long-term solution. The paper is still very print-focused but we're slowly pushing into more getting more web-specific content and as we do, we'll likely start looking at editing print articles for the web, which will likely be where workflow tools will especially come in handy.
With The Boar, we've started to shift some of our workflow online. While stuff is still copy-pasted over, we're using the draft functionality (as Emily mentioned) for some final stage editing and final approval from the EIC, at which point a post is published.
For a long time now, I've had the vision of developing a CMS that acts as a hub between the print and online editions. I think all content should be centrally stored in a manner that's kept up-to-date and distributable across formats (publish to web via XML-RFC, publish to InDesign/Quark/etc. via XML). Ours is scattered everywhere, across emails, networked drives, different file formats, and it's all a mess really. Of course, building such a system is easier said than done.
I wanted to point out an app started by some former college journalists called writewith which was built initially as a writing workflow tool for journalists. It's a fascinating tool and I think there's a lot that you can pick up from it for building a WordPress workflow plugin. It's still online, though it seems like the development is defunct. There are obvious problems with it, namely that a lot of work (namely copyediting) is still done best offline. But there are ways to work with/around these.
So I guess as a summary of my rambling, I'm all for a digital newsroom like Populous — one that combines story and asset management and publishing (to both print and web). In the end though, I guess it depends on the needs/culture of your newsroom and any workflow changes you do make, do so gradually. A former EIC of Imprint a few years back built an app much like Miles' that helped manage story assignments; but come launch time he backed out and dropped the project saying, "The volunteers just aren't ready for it."