It works the same way as Voice Search has always worked (at least since Froyo): The found action is shown to you for about 3 seconds along with a timed progress meter (3 seconds?) and buttons to proceed or cancel. When the timer ends, the action proceeds.
This is the correct solution, IMO. It would be quite frustrating to have the wrong phone number instantly begin to dial, for instance. One time when I said "call <name of restaurant>", it came up with "Call <name of restaurant>" with the address of the location I didn't want shown beneath. This gave me time to tap Cancel, which then showed me a list of the alternative results/locations.
So lets say you have your phone in your bag, not looking at it. Then you enable the voice command and say "Call Foo Burgers"
Your phone understands this as "Call Bar Burgers" and shows on the screen "Calling Bar Burgers". The phone makes a "beep" sound and then proceeds to show a progress bar which you don't see because your phone is in your pocket.
Then the phone connects and you learn of your mistake as the person at the other end answers with "This is Bar burgers, Mr. Foobar speaking".
The only way around this is to enable the voice command, take the phone out of your pocket and then check what it says above the progress bar.
With siri, if you say "Call Foo Burgers", Siri would respond (in audio over your headphones) with "Calling Bar Burgers", giving you a chance to cancel before you annoy the person at the other end and without forcing you to take the phone out of your pocket to check (which is the point of voice commands)
This is the correct solution, IMO. It would be quite frustrating to have the wrong phone number instantly begin to dial, for instance. One time when I said "call <name of restaurant>", it came up with "Call <name of restaurant>" with the address of the location I didn't want shown beneath. This gave me time to tap Cancel, which then showed me a list of the alternative results/locations.