from my anecdotal experience: having anything other than a hard redirect entirely misses the point of this feature. A click or waiting 10 seconds pretty much nullifies all the benefit. I think an opt-out is the best way to go. Any technical enough user that is bothered by it should be competent enough to disable it or be aware what happens when they are trying to get general information.

Observing my dad using his iPad, he regularly types sites without the TLD with his only intention being to get over to facebook.com