There are some pictures of the junior suites on the CSR thread. They are the size of two rooms and have either a king or two queens in the bedroom and a pullout in the living room. There are two bathrooms. A couple of people on the CSR thread have been upgraded to a junior suite, but that is uncommon.
We had initially booked a junior suite for our trip last month, but we found it was less expensive to rent points and book a 2 BR villa, so we changed our reservation.
The junior suite was about the same price as a standard room at Poly for our June dates, but the junior suites had more room and two bathrooms. The beds at CSR are more comfortable than the beds at Poly as well, but the Poly has better dining choices and also has the monorail. A standard room at Poly sleeps five, but the junior suites sleep six.
Cheaper two-room options onsite are the family suites at All Stars and Art of Animation or the Ft. Wilderness Cabins. Renting points for a 1 BR (sleeps up to five, depending on the resort) would also be cheaper.
We love CSR and think it is a great value for the price paid, but we usually book one room. The junior suites are a bit more than the price of two rooms, but you are guaranteed to have the space together (while connecting rooms are just a request).