Manpower is an excellent place to learn almost any office skill you may need in the future. You definitely deal with a little bit of everything- sales, customer service, accounts receivable/payable, payroll, staffing, recruiting, compliance, etc, but the work life balance is near non existent. There is a pattern in corporate of understaffing all of the local branches, so you are generally saddled with intense workload, as well as associates out on jobs all hours of the day, night, and weekends. If a customer needs someone on a Saturday, you're expected to jump. Corporate also does not make it easy to obtain the information you need to fix problems, and sometimes makes it near impossible to get from point a to point b without losing your mind.
Also, they keep most of the recruiters in the company as "internal temps" for upwards of 2 years or so, basically avoiding giving their own employees paid time off or decent benefits. the pay is not bad and you end up working with some great people doing interesting things, but you should definitely weigh the pros against the cons!