I think overall there's a general feeling among brokers that they are working for the landlords. The "good" brokers realize that they are working for YOU, because you are the one paying them. If you get a broker who isn't on your side, then fire that broker and go and get one that will work for you.
In our experience with brokers we found that nearly all of them work for the landlord (on their side), but of course want you to pay them. I've never found a broker I was happy with, though it's been a few years since we used one. We did end up renting our first apartment through a broker, but once you live here I think it's much more worth it to spend some time canvasing the streets and talking to locals to see what's available. How do you think brokers find the empty houses? Just become your own broker and save the money.
A friend of mine found an interesting way to put the broker to work for him. After he found out the price of the apartment he wanted he asked the broker to get a lower price, which of course the broker (who is working for the landlord) said that they couldn't go lower (besides, it's not in the interest of the broker to negotiate a lower rent for you, the person who is paying them, because they get a bigger commission based on a bigger rent for you [so twisted]). So he said he'd give a 200% bonus commission on every dollar the broker negotiated off the monthly lease. In other words, if the broker lowered the rent $50, then he gets an extra $100 in commissions. Surprise, surprise, the rent was lowered $200/month. Broker got an extra $400, but that paid for itself in no time.
The way this city works is really screwed up sometimes. Only in NYC do renters have to pay brokers who work for the interests of the landlord. What a joke.