My personal experience working at The Right Thing has been fantastic.
Pros
The Right Thing is a scalable organization - what this means to part time employees is that they have an enormous amount of flexibility in how they want to set their own hours. Full times employees also have a lot of flexibility with how they structure their days, especially if you need to leave work for a doctor's appointment or have a child become sick unexpectedly at daycare. Overall, I have found the level of management and dedication to the needs of the employees to be higher than anywhere else I have worked.
Cons
The down side of scalability is that there is not a guarantee of hours for part time employees. If buiness slows, you may not be able to work all of the hours that you wish to work, although in most cases you will retain a minimum amount of hours. During an hours slowdown, full time employees may find themselves working extra hours to help cover tasks normally done by part time employees.