If you are looking for unsure about the quality of this program, this rest assure it is outstanding. The teachers are experienced, professional, and 100% friendly (I had lunch and dinner with all of them, and traveled with some around China).
If you are worried about your IES friends that will accompany you, then don't. IES knows (for real) how to pick the best group of people. Those people made the experience even more enjoyable. We took care of each other, and we encouraged each other to learn and venture for fun.
If you are not sure about the city, then don't. I came to Bejing thinking about all I heard regarding pollution and wearing masks. Fact: I never wore a mask for any health concern, and trust me I do take care of myself. This trip made understand Beijing real situation and for that I'm grateful.
Language: you will learn a lot.
Fun: Everyday is a new adventure. There has not been a single boring day. (Probably it's the case of study abroad).
Food: you will definitely fell in love with it. (Contrary to what some tourists might say because you will emerge in the culture and gain the real perspective).
In short, If you remotely thinking about this program, stop and just do it!