Yeah, I've done that, but it's not quite what I had with my old dumb phone.
Best scenario: I press the BlueTooth button on the BlueTooth headset and it kicks off the voice dialer. I say who I want to call, it reads the entry to me, I verbally confirm, and the call is placed. I used to be able to do exactly that with my old LG. Note that I never even touch the phone itself.
Second-best scenario is that I have to press a button on the phone to start the above process.
The scenario I have, however, is the following: Press the power button on the phone to wake it up. Slide the unlock icon across the screen to unlock the screen. (This can be disabled with the 'Awake Stay' widget.) Press the 'Voice Dial' shortcut on the main screen. It finds the match and prompts me on the phone screen if it's the right number. I have to acknowledge by pressing on the phone screen. Note that this is a lot more heads-down on the phone than what I used to have. And my car doesn't have autopilot!
The solution would seem to require better BlueTooth integration (to be able to use the BlueTooth device to start an application) and a better voice dialing application. So it doesn't seem insurmountable, and I expect it to be fixed at some point.