Added option to limit number of recipients per e-mail. Once the limit is reached, the recipient list will be broken up and the mail sent out in pieces. This may help some of the issues raised re: mail not sending.
Added error tracking and detailed logging via drupal_set_message
Version 1.1 of the update status module will try to guess at the project your modules from CVS come from (as well as very old modules from drupal.org); it also allows you to turn off notification for particular modules. It also fixes some UI bugs and adds functionality to the interface.
Version 1.2 fixes the notification part of this, which was a little bit broken.