After seeing some of the problems that Microsoft has had upgrading people from Internet Explorer 6 and also seeing how Firefox has automatic updates, it\'s made me consider the
Yes and No.
To be clear, it should be an opt in. You want auto-updates, you can select auto-updates. You will run into some implementation issues/limitations, but that is for another question.
I can see a mix, some users may prefer to have security updates pushed, but not a new version. Other may want both, some neither. If you keep it flexible, this could be the one distinguishing features of your CMS.