My understanding: TACC and AEB is that they work independently of each other. I use TACC all the time and it does an excellent job in managing safe distance, especially in v7 where it has been greatly improved. AEB I've only experienced a few times, it's scary because AEB kicks in near last-minute, right at the time where, once you realize it, you'd end up slamming on the brakes anyway. AEB kicks in moments before you do if you weren't paying attention. Though, I think it wont take you to a complete stop, I think it just slows you down so that instead of smashing into the car in front of you, you'll end up hitting it at under 9 MPH. Hopefully by that time you'll have smashed the brakes on yourself.
FYI ... I now use AutoPilot for 99% of my freeway driving and it's freaking awesome. The chance of an accident caused by me is further reduced because of it. Keep your hands on the steering wheel at all times.