Here is my experience as a medical student on general surgery, others may have different experiences. Also, keep in mind that students do not work nearly the hours that residents work. There is one gen surg resident lurking around these boards, and he might be able to give you more details.
Start every morning around 6, work until 6 or 7 at night. Every third or fourth night on call (on average). On call - you work all day, all night, and all the following day. You may get to sleep a little on call, but rarely do you get any meaningful sleep. I kept track of how many hours i was in the hospital during my gen surg rotations. My lowest was around 75/week, the highest was 115.
So, yes, the 80-100 you read about is true (and it does include call). At my hospital the senior residents do have it slightly easier than the juniors. They do call from home and back up the juniors when they need help. However, they usually end up in the hospital for most of the night, so it's not really much better.