Are temporary agencies such as Manpower and Hamilton Ryker worth working for?

I have had very good experiences with temp agencies. Most of my working career I worked through those agencies. I have gotten several permanent jobs (including the one I am on now) working temp first. Often people complain that the agency takes half your earnings. If the job is paying you $10 an hr. then they are making $10 an hour too. But I don't bother thinking of that because they have to make something in order to keep the agency going and paying their staff. I also like it because if the boss is a pain then it is not a problem because you can leave or either deal with it knowing that the assignment wont be too long.