I participated in a 2 month internship + 21 day trip (with The Dragon Trip), and overall enjoyed my experience. The program, like most things, is really about what you make of it. I wanted a summer abroad (I had good internship experience previously, so I wasn't as concerned with placements), and China was on my list. Shanghai is a vast and rapidly-developing city, and you could spend all of your time just picking one metro stop at a time and exploring.
The internship placement was pretty good, but depends on staff and fellow interns (I began with a good cohort, and towards the end of my internship many positions rotated, so it was less enjoyable/interesting). Accommodation, at least for China, is very adequate. The hotel is close to the Metro, and is very spacious. You're in the city center, so it's quite convenient to get to most places (via the clean Metro or cheap taxis--beware of "black taxis" and other scams, however). CRCC Asia puts on a short orientation with incoming interns, and the staff is a mixture of foreign/local young people. Most were very responsive/friendly, and called me a few times during the program. That said, I never encountered any major problems, so I cannot speak to their response in a crisis situation.
During my two months in Shanghai, I picked up a bit of Chinese, but it's very possible to get by with basic to no Chinese language ability. However, I speak Japanese, so I was able to read and remember the Chinese characters on signs and instructions more easily than someone not familiar with Chinese/Japanese. Being that Shanghai looks toward Westernization, however, the food, shopping, and retail workers are likely to cater to foreigners. In this way, Shanghai may be an easier place to adapt to than Beijing. Air pollution was fair to slightly poor--no one wore masks but I did catch a cold/respiratory cough from it. Food is generally safe, unless you go after street food (which is dicey any place).
Safety was comparable to any major city (perhaps better?). Still, there doesn't seem to be an active homeless population, and I (as a white male) never felt threatened, but was treated as a minor celebrity/spectacle (which is harmless but annoying). The people I knew traveled in groups/alone, and never had any problems/harassment.
My 21 day The Dragon Trip was, overall, very interesting, and opened China to me in a previously-locked way. However, it was very physically demanding (hiking, miles of biking, extended train rides/overnight "sleeper" trains), and our particular small group got passed between two larger groups, which meant we had to forge new relationships every couple of days, which killed some of the potential camaraderie. However, the price was competitive for the accommodation/transport/admissions, and the floating mountains in the south, the city of Xi'an (and its terra cotta warriors), and other iconic locations were breathtaking and worth it.
My advice for the program is to temper and pinpoint your expectations. If you're goal is to get advanced experience in a very specific field, that cannot be guaranteed and you may be disappointed. However, if you're using the opportunity to travel and stay for an extended period in China, meet new people, or practice your Mandarin, the program gives you a fairly simple way (and a VISA, which can be difficult to obtain) to accomplish this. The trip is a "best of," and gives a good overview of the country, but it's certainly not exhaustive (and pretty no-frills). Either way, being an experienced traveler in non-Western countries gave me an advantage coping to the usual and un-usual cultural/political/logistical differences of life in China. However, Shanghai is a good access point for Westerners to China.