It depends what you mean. Do you have iDrive? (I could probably find out from your VO, but... I'm not going to
) In that case, voice control actually... does stuff. And you might want it. Otherwise, the voice control that comes with non-idrive bluetooth is super basic and pretty useless. It'll let you dial phone numbers directly, which is great if you have numbers memorized. It'll also let you dial names, but you have to manually put them in the car's phonebook - it listens to you saying the name and has a matching algorithm, rather than a more modern synthesis-and-matching algorithm to match, say, names it only knows the spelling of in your PHONE'S phonebook (which you can browse from the headunit).
Anyway, are you saying that when you click the voice button on the steering wheel it just... doesn't do anything?
edit: while we're at it, do you have an iPhone new enough to have siri? If so, that'll work over bluetooth, and will far outstrip built-in voice command usefulness, idrive or not.