Drupal Gardens is Acquia's Drupal 7 SaaS product.
Hosted and maintained Drupal - similar to Wordpress.com
It is promising, but is it ready for commercial use? There are already 10K+ DG sites!
Limitations such as no Calendar/Event modules are restricting its use, but it will surely grow in its capabilities in time.
Share your experiences - I am creating a community site for a school with DG, importing a static site with a custom theme and menu system. The client loves the idea of free hosting and maintenance! [note: the free service is limited in the amount of pages and data transfer, but there are other tiered commercial plans available]
There is no "official" session for Drupal Gardens - so let's flock together!