We have an online magazine and Web portal built with the .net framework, but powered by the article manager tool. Both the content management team and the development staff have been very happy with the article manager.
It would have been far more expensive to develop this functionality ourselves, and the tool really seems to have intelligently anticipated our publishing needs. Further, the helpdesk has been very supportive and informative, whenever needed (they seem to have coverage 7 days a week!)
Our editorial and writing staff have taken to the workscreens very quickly with little learning curve. They use it to maintain all our articles, as well as most of our static pages, such as media and corporate pages. Article manager also supports our RSS feed.
From an IT perspective, the article manager templates are flexible to work with, and allow fairly complex integration with the asp.net framework. We have a lot of site functionality not related to article publishing, that nonetheless has to integrate with the content coming out of article manager. This has gone smoothly.
The only feature that I wanted that was not available was the ability to store the article manager data in a standard database format, such as mysql or sql server. However, my understanding is that this feature will be available in the next release coming this fall, and for this reason, should be worth the upgrade for us.