When updating software, the user should always read the change log. However, I'd agree that an updated that will most likely break things should have some kind of additional notification (pop-up, bold/red text in the change log, etc). However, IMO this is not really that big a problem. For typical HG users, they would simply uninstall HG, run the installer for the old version, and restore the backup. If you don't have a backup, you are playing with fire and that is the user's fault, not the developer.