I've never personally been able to get any use out of the voice control feature of iOS. In fact, after trying it a few times, the only time I invoke it now is by accident. I hope that Apple kicks some major ass on this feature and creates another "how did I ever live without this" moment.
I use it while driving to call people without having to dial with my fingers. Unfortunately once the call is placed I still have to use my fingers to set it to speakerphone.
When I can ask my smartphone "what time is the next bus arriving?" without having to touch it, that's when it's a really smart phone. I hope it's that level of a kick.
A family member tried it on an original Droid, and it was a miserable failure for her. I was a bit mystified, comparing this experience with the positive comments I'd read. Might be her voice in particular; I turned on the "personalized tuning" setting, but it did no good.