As a part-time Contractor, I have absolutely flexible schedule. I may work at any time: late nights, overnights, weekends, holidays - whenever 24/7. Any days off for personal reason - no questions asked. Vacation is unlimited, could be taken any time with 3 weeks acknowledgement.
Cons
As a part-time Contractor, I have no Health Insurance. Vacation is unpaid. Training is good, but not always enough for new employees at the beginning.