When I was researching this program, I searched all over for recent reviews but couldn't really find any. For that reason, I was hesitant. I still took the plunge, however, and I've been in Vietnam for about two weeks now. CIEE provides great support along the way, and there have been no surprises—what you see is what you get, thankfully.
One of the main reasons I chose the program was a placement in Hanoi, which I've really enjoyed exploring since I got here. It's really hectic at first—overwhelming, really—but it's a lot of fun. I'd highly recommend checking out the Anthony Bourdain Parts Unknown episode beforehand, as it gives you a great feel for what the city is like.
CIEE's partner school in Hanoi is one of the best ones to work for as far as I can tell. It can certainly be disorganized at times, but it's hard to avoid that in this part of the world—be flexible and ready to roll with the punches! The staff have been really nice and supportive, but many things have a bit of a learning curve. They'll throw you into your own classes within a week of arriving, but they have a wealth of resources from which to draw. Also, the other teachers at the center have been nothing but friendly and helpful along the way.
The CIEE staff have been really responsive and accommodating, but the time difference (and correspondingly, work schedule) means it can take a while for questions to get answered since they must go through CIEE to the school. This is a really minor gripe, however. The included TEFL course was quite useful and exhaustive if a bit of a slog at times. Sure, you could do this all on your own for a lot less money, but CIEE provides so many failsafes that I found it really worthwhile. Overall, my experience has been about as seamless as possible (because certain aspects of the process will be byzantine no matter what you do), and I'm excited to spend a year living and working in Vietnam.