Indeed, it is one of the most useful features. No memorizing class names and APIs. Why would you want to turn that off? Type 'fl' and press it will autocomplete float for you. Major efficiency improvements, and you won't even notice it after a while.
I want the IDE to give me the option and not assume that I want it, or, at the very least, make it clear where to turn it off. I am having to go through the options dialog in a hit or miss fashion to find these "features". It took me two days of Google searching to find out how to hack the themes to get it to something that didn't hurt my eyes. I didn't have these issues with 2010, but I don't want to go back. The new language features make the upgrade somewhat worth it. It is still an incredibly frustrating transition.
An IDE should make it's most useful features on by default and not default to notepad + compiler. You are by far in the minority for wanting to disable an autocomplete feature.