Cons: contracted and work load varies drastically.
As a contracted Teacher's Assistant you mostly work alone. Your work load is very dependent on which Professor you are given.
Some range from Invigilation, exam correcting, tutoring, supervising etc..
Hardest part is if you are given a course you know very little about, and need to quickly learn the course load as you correct it.
Most enjoyable is – more... the level of independence given. – less