Hi Vishal,
The common answer to this would be that Temp Staffing has its own set of pros and cons.
However, much depends on the company hiring such services. Sure employees are a part of the third party vendor. Although HR Admin, Payroll, Help Desk, etc responsibilities lie with the agency, a few responsibilities have to be taken up by the client as well. Regular monitoring, maintanence of attendence, regular feedback to the third party vendor, etc are some of the duties to be taken up by the client.
Therefore, if used well this kind of hiring is very useful considering present market trends.
Regards,
Imran