I'm very happy to have used Drupal 5.1 in both of these instances, a little background:
BCbusinessonline.ca
BC Business Magazine, is an emerging scenario in the publishing world, as old-school paradigms shift to on-line publications, and in many cases play catch-up. The biggest challenge with this project is that they have several magazines that will be built along the way, so the dilemma was do we do two drupal sites, or one multi-site, using themes instead. There are benefits to both, performance being the greatest concern...
All the modules are standard drupal modules (CCK, Views, Panels), there's some remote flash integration and a few custom modules we wrote that provides more complex node scheduling. Which was integrated into panels via blocks, to provide "schedulable slots" for editors to slot articles.
We also integrated a third-party drupal module (the name escapes me), but is really amazing to integrate video and mp3 into a flash GUI as a CCK field.
Capers Markets (capersmarkets.com)