Uncle Sam was my very first teach-abroad experience after university, and I worked with them for a year. I spent my time at their Banqiao branch just outside the city center.
As far as the school and staff goes, I really could not ask for more supportive co-teachers. Everyone was very friendly and helpful, and the whole environment was family-like. The head teacher at my branch, Shirley, was so nice and responsive to the concerns of her foreign staff.
The amenities and teaching materials at the school were extensive and quite useful. We had plenty of toys and objects to use for games, and the school provided us with all the materials we would need for carrying out effective lessons. We were also allowed plenty of Internet access in the teacher's room to look for ideas. In addition, the school is extremely clean and quite high-tech compared to other places I've worked since then. Just walking in there, you will see an extensive PA and camera network, as well as video projectors, ridiculously good air conditioning, and massive stereo systems. There is even a phys. ed. room on the top floor.
One aspect of Uncle Sam that some might find difficult is how much work is required of their teachers. I found my job there to be quite demanding, starting at 8:30 and ending around 18:15 every day. Some days, we got long lunch breaks (2 hours), but others, we were busy with writing report cards, doing lesson plans, or participating in teacher meetings. Teachers are well-paid, but you are asked to take a very involved role in your teaching -- often writing evaluations, completing testing, and preparing students for competitions and big events. If you are looking for some serious teacher training and support, you will get it here, as well as a lot of practice with workshops and plenty of feedback from colleagues.
Once you settle into the school, however, a lot of this work comes more easily. If you are willing to put in the effort, you should be able to adjust to it. In addition, the students were fantastic and so lovely to teach. Overall, I learned a lot and had a really nice experience with my students and colleagues.