This is something I've been wanting to have done for a long time. Since I have to release a new version now, I have implemented it:
(http://forum-images.pixinsight.com/20140124/UpdateManager/new-version-notification.png)
Anyway, it never ceases to amaze me how a lot of users (hundreds, actually) either don't receive our notifications—outdated email addresses, spam filters—or simply ignore them.