I did the Celta here in Hanoi, Vietnam last November. I have a university degree from a very respectable engineering school from the states and the celta still kicked my ass.
Having said that, I need to clarify that it wasnt any one task that is hard, it is everything combined with being observed and critiqued so often along with doing the same for the other teachers-in-training that made it stressful.
I taught kids before the celta and have been teaching teens and adults since then, and I can tell you that this program has helped oodles more than I ever expected, and not just in being able to get better jobs, but in the classroom.
If you have any specific questions about the CELTA or taking it in Hanoi, please feel free to email me directly at dstephfuccio@yahoo.com.
Steph