We have created the new Fortrust website using Drupal 7. This was a great opportunity for our team to test and develop on Drupal 7.
Our key findings were that the administration and site development has been made more user intuitive and simpler. This definitely led to quicker work flow.
In terms of contributed modules then some of the key Drupal 6 contributed modules have been incorporated into the core modules like image. So now you can now add and manipulate images into content from the standard setup.
Theming is easier as you can control exactly what gets shown where on the screen with the new Render API and some truly radical alter hooks.