The good news is that auto updates at present only updates minor point security/bugfix updates. For example, the current version 3.7.1 will automatically update to 3.7.2 if there ever is one, which would be unlikely to break anything, but not to 3.8.0, which might render many plugins inoperable. Also, themes and plugins are only updated on an opt-in basis. The bad news, in their wisdom the folks at WordPress have failed to offer an easy way to disable this feature. There’s no way to turn auto updates off through the dashboard; it can only be disabled through editing configuration files and the options are not as straightforward as they should be.