I'm only responding to this and resurrecting the thread becuase it was one of the top results of my search....
I had the same issue, and fixed both GoogleNow and VTT (via my keyboard button) by going into GoogleNow Settings, selecting "Voice" and unchecking "Bluetooth Headset".
I think this means the phone will pick up my voice, rather than my vehicle's microphone.
That's it. I'm amazed how well GN works now.
For my Swype keyboard, when I click the mic button, I do have to click "Done" before it starts recording (ow *that* is intuitive) and then I can record perfectly, and click Done gain to finish recording.
I hope this helps some of ya'll out!