Wow, where to begin.
I can't talk about what CDI used to be like, prior to 2008, but I do know that since 2008 it is one of the most highly regarded schools in all of Korea.
I myself went through all of the training and jumped through all of their hoops, and all I can say is they never did anything that they didn't promise to do.
Training was hard, yes, but that is because they have very high standards and they expect you to learn a lot in one week. Hard, definitely, but not unrealistic. One of the tests they make you do is a grammar test. Well anyone born and educated in the US or in Canada knows that we are horrible at grammar! Unfortunately our education systems did not focus on our grammar, at least not during the 70-90's. So trying to learn 8 knew grammar things over night is difficult, for anyone! I suggest that if you are thinking about doing ESL, brush up on your grammar!
As for the mock teaching, being a trained and experienced teacher in the West, the training at CDI is great.
It is intense but they teach you very useful skills. It is like a nutshell version of Teachers College.
YES you DO get a certificate! I have one!

I have gone through Teacher's College back home and it was difficult! The good ones are!
Teaching and communicating are incredibly complex skills and not something to be learned or grasped over night.
I am not saying that after the week of CDI training you will suddenly be an excellent and confident teacher, but man oh man will it help! I actually experienced a co-worker who for reasons not important, missed out on their training and they did have a much more difficult time.

Then there is the complaint about the non payed holidays. Yeah, it sucks, BUT, they never promised they would be!
Basically, if you are going to work for ANY company, all I can say is research it and read the entire contract!
If they say no holidays, they mean it. Be prepared for it, but don't wine about it after you sign up!

Last part, the key money is real, and once again, they state right on their forms that it is a loan.

Bottom line, I had a positive experience teaching with CDI.
So much so that I convinced my brother and my best friend to come over and join me, all of us working for CDI.
We all enjoyed our time.
Yes there are difficult times but that is life!
No job is perfect, especially when you are working with people!

My brother is still there after 3 years, is planning to remain for many more, and I myself after taking a 1 year travelling vacation, am on my way back to Korea, to once again work with CDI!

I just wanted to set a few things straight and shine a positive light on CDI, since pretty much everyone else here is so negative.