There is everything wrong with autoupdate, basically you are giving whoever controls the updates full control over your software and data, with autoupdates it is possible to:
Autoupdate has always been used for bad, its purpose was always to take control away from the user, updating should ALWAYS be a choice.
Source:
I hope he doesn't mind me reposting this. And let me add modifying user settings to the list of auto-update issues - something which Firefox has done many times, for example.