The Komodo Community site has been running Drupal for quiet some time. At OpenKomodo.com, Jeff posted a interesting article on a few quick tips to get the cool-ness of Komodo for your Drupal work see: http://www.openkomodo.com/blogs/jeffg/setting-komodo-edit-drupal-develop.... I make use of Komodo IDE at work and Komodo Edit at home.
I have not tried Netbeans that was so recently discussed on the Development mailing list, but not sure anyone can convince me to give up this tool.
I have released the first versions of both of Content Recommendation Engine and Similarity Objects. These modules, while appearing to be duplicates of other modules, are a significant departure from them. Most notably, there use of Views 2 and thus, respecting node_access() which is lacking in most of these modules or it is done after the query is sent to the database. Please read on to find out why I believe both these module provide more functionality then anything like them.