We were on the SWC during Thanksgiving, and the temperature in the car was WAY too warm due to a heater malfunction. Our SCA turned it off so we wouldn't cook in our rooms, so our room got down to about 65 that night. We didn't mind since we usually set our heat to 64 at night, but I know some people were cold. Normally, you can use the dial to adjust the temperature in your room, but since the SCA shut the heat off completely, it couldn't be adjusted at all. (Not that it would have mattered, as the thermostat for the car wasn't working.)
Even though the sleepers were full to capacity, our SCA told us there were plenty of extra blankets and pillows if we needed them. As a side/stomach sleeper, I thought the pillow was the perfect thickness, but it might not be thick enough if you're a back sleeper.
I wasn't sure what the temperature would be like since this was our first time in a sleeper, so I did pack a long-sleeve shirt to wear under my sleep t-shirt if necessary. I also had a pair of flannel pajama pants and some fuzzy socks. I was planning to wear the long-sleeve shirt during our trip and the pajamas and fuzzy socks around the "in-laws'" house, so it was a good way to be prepared for a cold night without actually having to pack extra items.
I found the bed to be comfortable enough for a night or two, but it's definitely not a Serta.
I had the bottom bunk, which has a bit more cushioning since they put the mattress on top of the seats. The top bunk just has a mattress and is a bit more like a bed roll you'd use while camping. My boyfriend likes firm mattresses, so he slept well, but if you prefer a softer mattress, sleep on the bottom bunk.
Tip: if you are a side sleeper, leave the blankets tucked in to help prevent as much rocking as possible. I didn't sleep well the first night because I was getting rocked/tossed so much. The second night, I left the blankets tucked in and shimmied down into them like a sleeping bag cocoon. I slept on my stomach instead of my side too. That did the trick. I didn't feel as much lurching, and I only woke up a couple times.