can summarize the message as "The contributions/modules directory, rather than sandboxes, is the right place for (experimental or otherwise) code for contrib modules".
But this will not answer the need for mfredrickson's vews patches , and other experimental code that is not even meant to be released ever. To answer Steven's concerns, his starting "If you used the sandbox before simply as a means of revision control," is false. These code often are not version controlled because they see only one commit. Which words of I am using the sandbox to share my experimental code with the Drupal community can not be understood? The userstag module I checked in 2005 autumn and was contacted maybe a month ago by someone who needed it and ported it to 4.7. More on Steven's letter: "many developers now have personal revision control systems, either hosted or distributed" -- yes, distributed, hard to reach, not on Drupal's infrastructure.
The sandbox as it is now is one big pile of code... mostly crap, with some active pieces buried in it.
Yes! It is! Keep it so! To use the words of Tolkien: "All that is gold does not glitter". Who can say what's crap and what's not? Do not even bother. Regards NK Ps. If you think I am frustrated, I am not. I am only sad.