Pros
I started with Metroproof 4+ years ago, and have the pleasure to say that they are some of the best people I've ever met. It's a tightly-run temporary staffing agency that provides proofreading and editorial services for ad, legal, and medical clients.
They have some seriously rough tests to pass to join their team, but they are generous and open-minded, and their doors swing wide to welcome good folks into their fold.
The key point is that the management is judicious, yet flexible. Whether you're a new proofreader that just took a course, or a veteran of whatever circumstance unemployment has inflicted, these folks will always take a look at you from every angle.
Getting new and proven proofreaders and editors the opportunities they need to succeed, and knowing their clients inside and out, is the nature of their business.
Though I did not end up being a proofreader for them (I did not pass their ad test), a few weeks after I tested I was contacted for a position on their staff. I ran with it, and I have zero regrets.
They are highly selective in their talent sourcing, and potential proofers and staffers will have to run the gauntlet of several interviews to get on board, but that's the genius in how they work.
Their job is knowing who's right for whom, and knowing a person's temperament and veracity is something they don't take lightly.
I'm a little bit of an insider now, since I'm on the staff, but I have nothing but good to say about the proofers that pass the mark and get in.
This is not a sprawling company where you can't get an ear. The core staff is small—and intentionally so—because the owner is dedicated to such. His guidance and input on everything from rèsumè-building to permanent placement and negotiating salaries for temps that clients want to take on permanently are right on.
This is a company that cares for its people.
Cons
As a staffer, I'd like to see more of the internal office-use paperwork digitized.
Staffer pay isn't spectacular. No health bennies for part-timers.