Manpower subcontract you to different companies so the work will vary from place to place. I found my subcontracted company to be very helpful/friendly people.
I had little communication with Manpower, from an employee`s perspective they left me with little faith in them. There was miscommunication from the outset, wrong hours advertised, hourly rates wrong and a complete lack of transparency with the company. I never had issues which were out of the ordinary, a random small pay, a weird question about my bonus or my holiday pay structure... It would take weeks for replies, really simple issues would become a big deal. The staff at manpower seem to enjoy the idea of promoting hard working individuals but take none of their teachings on board. The company i was subcontracted to picked up so much of Manpower`s slack. I think anyone can work for Manpower, but after 12 months of silly mistakes most people will wonder why they work for such unqualified people.
If you need a job, Manpower will get you some work, if you want something long term with a decent employer, id say to keep looking.