Pros
You can choose to work whenever you want to (if jobs are available) and you can work for multiple districts if they all use Source4Teachers.
Kontras
They recently implemented a terrible concept to help out schools fill specific positions by only making district-wide jobs available and not specifying the specific job or school. So if you are trying to get experience in a high school, you may often get put into an elementary school. Or if you prefer to not work in a special education classroom, you may get put into a special education classroom. I understand the thought process behind what they are trying to do for the schools, but in the end I think it is really hurting the classrooms and making it worse for the employees as well. They also don't update the teacher lists for all the schools every year. So you may take a job for a certain teacher, show up to the school listed, and find out they don't work at that location anymore and they actually work at a different school. And many participating districts still use their own list of substitutes instead of putting their jobs on Source4Teachers.