The pros heavily depend on your host facility, program manager and mentor. My mentor is great and allows me lots of freedom to do my work and develop my skills. Depending on your host facility you get to work with federal agencies and potentially get connections for a permanent job.
Cons
We are considered not employed, but a "participant in a program". Our salary is a taxable income. There is no benefits other than an offered health insurance that costs hundreds each month out of your salary for minimal coverage. There is no PTO. You have to ask permission if you want to take a day off or go on a trip. Any problems with the management goes unnoticed and you get told by ORISE to speak to the program manager even if they are the problem.